diff --git a/java/AndroidManifest.xml b/java/AndroidManifest.xml
index a1ffe5a..054c415 100644
--- a/java/AndroidManifest.xml
+++ b/java/AndroidManifest.xml
@@ -18,7 +18,7 @@
         coreApp="true"
         package="com.android.inputmethod.latin">
 
-    <uses-sdk android:minSdkVersion="14" android:targetSdkVersion="19" />
+    <uses-sdk android:minSdkVersion="14" android:targetSdkVersion="21" />
 
     <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
     <uses-permission android:name="android.permission.DOWNLOAD_WITHOUT_NOTIFICATION" />
diff --git a/java/src/com/android/inputmethod/latin/DictionaryFacilitator.java b/java/src/com/android/inputmethod/latin/DictionaryFacilitator.java
index c205466..eced45e 100644
--- a/java/src/com/android/inputmethod/latin/DictionaryFacilitator.java
+++ b/java/src/com/android/inputmethod/latin/DictionaryFacilitator.java
@@ -61,9 +61,9 @@
     // dictionary.
     private static final int CAPITALIZED_FORM_MAX_PROBABILITY_FOR_INSERT = 140;
 
-    private DictionaryGroup mDictionaryGroup = new DictionaryGroup();
+    private DictionaryGroup[] mDictionaryGroups = new DictionaryGroup[] { new DictionaryGroup() };
     private boolean mIsUserDictEnabled = false;
-    private volatile CountDownLatch mLatchForWaitingLoadingMainDictionary = new CountDownLatch(0);
+    private volatile CountDownLatch mLatchForWaitingLoadingMainDictionaries = new CountDownLatch(0);
     // To synchronize assigning mDictionaryGroup to ensure closing dictionaries.
     private final Object mLock = new Object();
     private final DistracterFilter mDistracterFilter;
@@ -193,8 +193,9 @@
         mPersonalizationHelper.setIsMonolingualUser(isMonolingualUser);
     }
 
+    // TODO: remove this, replace with version returning multiple locales
     public Locale getLocale() {
-        return mDictionaryGroup.mLocale;
+        return mDictionaryGroups[0].mLocale;
     }
 
     private static ExpandableBinaryDictionary getSubDict(final String dictType,
@@ -226,6 +227,21 @@
                 usePersonalizedDicts, forceReloadMainDictionary, listener, "" /* dictNamePrefix */);
     }
 
+    private DictionaryGroup findDictionaryGroupWithLocale(final DictionaryGroup[] dictionaryGroups,
+            final Locale locale) {
+        for (int i = 0; i < dictionaryGroups.length; ++i) {
+            if (locale.equals(dictionaryGroups[i].mLocale)) {
+                return dictionaryGroups[i];
+            }
+        }
+        return null;
+    }
+
+    private DictionaryGroup getDictionaryGroupForActiveLanguage() {
+        // TODO: implement this
+        return mDictionaryGroups[0];
+    }
+
     public void resetDictionariesWithDictNamePrefix(final Context context,
             final Locale newLocaleToUse,
             final boolean useContactsDict, final boolean usePersonalizedDicts,
@@ -252,7 +268,7 @@
             final ArrayList<String> dictsForLocale = new ArrayList<>();
             existingDictsToCleanup.put(newLocale, dictsForLocale);
             final DictionaryGroup currentDictionaryGroupForLocale =
-                    newLocale.equals(mDictionaryGroup.mLocale) ? mDictionaryGroup : null;
+                    findDictionaryGroupWithLocale(mDictionaryGroups, newLocale);
             if (null == currentDictionaryGroupForLocale) {
                 continue;
             }
@@ -266,10 +282,11 @@
             }
         }
 
-        final HashMap<Locale, DictionaryGroup> newDictionaryGroups = new HashMap<>();
-        for (final Locale newLocale : newLocales) {
+        final DictionaryGroup[] newDictionaryGroups = new DictionaryGroup[newLocales.length];
+        for (int i = 0; i < newLocales.length; ++i) {
+            final Locale newLocale = newLocales[i];
             final DictionaryGroup dictionaryGroupForLocale =
-                    newLocale.equals(mDictionaryGroup.mLocale) ? mDictionaryGroup : null;
+                    findDictionaryGroupWithLocale(mDictionaryGroups, newLocale);
             final ArrayList<String> dictsToCleanupForLocale = existingDictsToCleanup.get(newLocale);
             final boolean noExistingDictsForThisLocale = (null == dictionaryGroupForLocale);
 
@@ -297,30 +314,29 @@
                 }
                 subDicts.put(subDictType, subDict);
             }
-            newDictionaryGroups.put(newLocale, new DictionaryGroup(newLocale, mainDict, subDicts));
+            newDictionaryGroups[i] = new DictionaryGroup(newLocale, mainDict, subDicts);
         }
 
         // Replace Dictionaries.
-        // TODO: use multiple locales.
-        final DictionaryGroup newDictionaryGroup = newDictionaryGroups.get(newLocaleToUse);
-        final DictionaryGroup oldDictionaryGroup;
+        final DictionaryGroup[] oldDictionaryGroups;
         synchronized (mLock) {
-            oldDictionaryGroup = mDictionaryGroup;
-            mDictionaryGroup = newDictionaryGroup;
+            oldDictionaryGroups = mDictionaryGroups;
+            mDictionaryGroups = newDictionaryGroups;
             mIsUserDictEnabled = UserBinaryDictionary.isEnabled(context);
-            if (null == newDictionaryGroup.getDict(Dictionary.TYPE_MAIN)) {
+            if (hasAtLeastOneUninitializedMainDictionary()) {
                 asyncReloadUninitializedMainDictionaries(context, newLocales, listener);
             }
         }
         if (listener != null) {
-            listener.onUpdateMainDictionaryAvailability(hasInitializedMainDictionary());
+            listener.onUpdateMainDictionaryAvailability(hasAtLeastOneInitializedMainDictionary());
         }
 
         // Clean up old dictionaries.
         for (final Locale localeToCleanUp : existingDictsToCleanup.keySet()) {
             final ArrayList<String> dictTypesToCleanUp =
                     existingDictsToCleanup.get(localeToCleanUp);
-            final DictionaryGroup dictionarySetToCleanup = oldDictionaryGroup;
+            final DictionaryGroup dictionarySetToCleanup =
+                    findDictionaryGroupWithLocale(oldDictionaryGroups, localeToCleanUp);
             for (final String dictType : dictTypesToCleanUp) {
                 dictionarySetToCleanup.closeDict(dictType);
             }
@@ -330,12 +346,18 @@
     private void asyncReloadUninitializedMainDictionaries(final Context context,
             final Locale[] locales, final DictionaryInitializationListener listener) {
         final CountDownLatch latchForWaitingLoadingMainDictionary = new CountDownLatch(1);
-        mLatchForWaitingLoadingMainDictionary = latchForWaitingLoadingMainDictionary;
+        mLatchForWaitingLoadingMainDictionaries = latchForWaitingLoadingMainDictionary;
         ExecutorUtils.getExecutor("InitializeBinaryDictionary").execute(new Runnable() {
             @Override
             public void run() {
                 for (final Locale locale : locales) {
-                    final DictionaryGroup dictionaryGroup = mDictionaryGroup;
+                    final DictionaryGroup dictionaryGroup =
+                            findDictionaryGroupWithLocale(mDictionaryGroups, locale);
+                    if (null == dictionaryGroup) {
+                        // This should never happen, but better safe than crashy
+                        Log.w(TAG, "Expected a dictionary group for " + locale + " but none found");
+                        continue;
+                    }
                     final Dictionary mainDict =
                             DictionaryFactory.createMainDictionaryFromManager(context, locale);
                     synchronized (mLock) {
@@ -348,7 +370,8 @@
                     }
                 }
                 if (listener != null) {
-                    listener.onUpdateMainDictionaryAvailability(hasInitializedMainDictionary());
+                    listener.onUpdateMainDictionaryAvailability(
+                            hasAtLeastOneInitializedMainDictionary());
                 }
                 latchForWaitingLoadingMainDictionary.countDown();
             }
@@ -381,17 +404,20 @@
                 subDicts.put(dictType, dict);
             }
         }
-        mDictionaryGroup = new DictionaryGroup(locale, mainDictionary, subDicts);
+        mDictionaryGroups = new DictionaryGroup[] {
+                new DictionaryGroup(locale, mainDictionary, subDicts) };
     }
 
     public void closeDictionaries() {
-        final DictionaryGroup dictionaryGroup;
+        final DictionaryGroup[] dictionaryGroups;
         synchronized (mLock) {
-            dictionaryGroup = mDictionaryGroup;
-            mDictionaryGroup = new DictionaryGroup();
+            dictionaryGroups = mDictionaryGroups;
+            mDictionaryGroups = new DictionaryGroup[] { new DictionaryGroup() };
         }
-        for (final String dictType : DICT_TYPES_ORDERED_TO_GET_SUGGESTIONS) {
-            dictionaryGroup.closeDict(dictType);
+        for (final DictionaryGroup dictionaryGroup : dictionaryGroups) {
+            for (final String dictType : DICT_TYPES_ORDERED_TO_GET_SUGGESTIONS) {
+                dictionaryGroup.closeDict(dictType);
+            }
         }
         mDistracterFilter.close();
         if (mPersonalizationHelper != null) {
@@ -401,40 +427,71 @@
 
     @UsedForTesting
     public ExpandableBinaryDictionary getSubDictForTesting(final String dictName) {
-        return mDictionaryGroup.getSubDict(dictName);
+        return mDictionaryGroups[0].getSubDict(dictName);
     }
 
-    // The main dictionary could have been loaded asynchronously.  Don't cache the return value
-    // of this method.
-    public boolean hasInitializedMainDictionary() {
-        final Dictionary mainDict = mDictionaryGroup.getDict(Dictionary.TYPE_MAIN);
-        return mainDict != null && mainDict.isInitialized();
+    // The main dictionaries are loaded asynchronously.  Don't cache the return value
+    // of these methods.
+    public boolean hasAtLeastOneInitializedMainDictionary() {
+        final DictionaryGroup[] dictionaryGroups = mDictionaryGroups;
+        for (final DictionaryGroup dictionaryGroup : dictionaryGroups) {
+            final Dictionary mainDict = dictionaryGroup.getDict(Dictionary.TYPE_MAIN);
+            if (mainDict != null && mainDict.isInitialized()) {
+                return true;
+            }
+        }
+        return false;
+    }
+
+    public boolean hasAtLeastOneUninitializedMainDictionary() {
+        final DictionaryGroup[] dictionaryGroups = mDictionaryGroups;
+        for (final DictionaryGroup dictionaryGroup : dictionaryGroups) {
+            final Dictionary mainDict = dictionaryGroup.getDict(Dictionary.TYPE_MAIN);
+            if (mainDict == null || !mainDict.isInitialized()) {
+                return true;
+            }
+        }
+        return false;
     }
 
     public boolean hasPersonalizationDictionary() {
-        return mDictionaryGroup.hasDict(Dictionary.TYPE_PERSONALIZATION);
+        final DictionaryGroup[] dictionaryGroups = mDictionaryGroups;
+        for (final DictionaryGroup dictionaryGroup : dictionaryGroups) {
+            if (dictionaryGroup.hasDict(Dictionary.TYPE_PERSONALIZATION)) {
+                return true;
+            }
+        }
+        return false;
     }
 
     public void flushPersonalizationDictionary() {
-        final ExpandableBinaryDictionary personalizationDictUsedForSuggestion =
-                mDictionaryGroup.getSubDict(Dictionary.TYPE_PERSONALIZATION);
+        final HashSet<ExpandableBinaryDictionary> personalizationDictsUsedForSuggestion =
+                new HashSet<>();
+        final DictionaryGroup[] dictionaryGroups = mDictionaryGroups;
+        for (final DictionaryGroup dictionaryGroup : dictionaryGroups) {
+            final ExpandableBinaryDictionary personalizationDictUsedForSuggestion =
+                    dictionaryGroup.getSubDict(Dictionary.TYPE_PERSONALIZATION);
+            personalizationDictsUsedForSuggestion.add(personalizationDictUsedForSuggestion);
+        }
         mPersonalizationHelper.flushPersonalizationDictionariesToUpdate(
-                personalizationDictUsedForSuggestion);
+                personalizationDictsUsedForSuggestion);
         mDistracterFilter.close();
     }
 
-    public void waitForLoadingMainDictionary(final long timeout, final TimeUnit unit)
+    public void waitForLoadingMainDictionaries(final long timeout, final TimeUnit unit)
             throws InterruptedException {
-        mLatchForWaitingLoadingMainDictionary.await(timeout, unit);
+        mLatchForWaitingLoadingMainDictionaries.await(timeout, unit);
     }
 
     @UsedForTesting
     public void waitForLoadingDictionariesForTesting(final long timeout, final TimeUnit unit)
             throws InterruptedException {
-        waitForLoadingMainDictionary(timeout, unit);
-        final Map<String, ExpandableBinaryDictionary> dictMap = mDictionaryGroup.mSubDictMap;
-        for (final ExpandableBinaryDictionary dict : dictMap.values()) {
-            dict.waitAllTasksForTests();
+        waitForLoadingMainDictionaries(timeout, unit);
+        final DictionaryGroup[] dictionaryGroups = mDictionaryGroups;
+        for (final DictionaryGroup dictionaryGroup : dictionaryGroups) {
+            for (final ExpandableBinaryDictionary dict : dictionaryGroup.mSubDictMap.values()) {
+                dict.waitAllTasksForTests();
+            }
         }
     }
 
@@ -453,7 +510,7 @@
     public void addToUserHistory(final String suggestion, final boolean wasAutoCapitalized,
             final PrevWordsInfo prevWordsInfo, final int timeStampInSeconds,
             final boolean blockPotentiallyOffensive) {
-        final DictionaryGroup dictionaryGroup = mDictionaryGroup;
+        final DictionaryGroup dictionaryGroup = getDictionaryGroupForActiveLanguage();
         final String[] words = suggestion.split(Constants.WORD_SEPARATOR);
         PrevWordsInfo prevWordsInfoForCurrentWord = prevWordsInfo;
         for (int i = 0; i < words.length; i++) {
@@ -520,7 +577,8 @@
     }
 
     private void removeWord(final String dictName, final String word) {
-        final ExpandableBinaryDictionary dictionary = mDictionaryGroup.getSubDict(dictName);
+        final ExpandableBinaryDictionary dictionary =
+                getDictionaryGroupForActiveLanguage().getSubDict(dictName);
         if (dictionary != null) {
             dictionary.removeUnigramEntryDynamically(word);
         }
@@ -536,20 +594,22 @@
     public SuggestionResults getSuggestionResults(final WordComposer composer,
             final PrevWordsInfo prevWordsInfo, final ProximityInfo proximityInfo,
             final SettingsValuesForSuggestion settingsValuesForSuggestion, final int sessionId) {
-        final DictionaryGroup dictionaryGroup = mDictionaryGroup;
+        final DictionaryGroup[] dictionaryGroups = mDictionaryGroups;
         final SuggestionResults suggestionResults =
                 new SuggestionResults(SuggestedWords.MAX_SUGGESTIONS);
         final float[] languageWeight = new float[] { Dictionary.NOT_A_LANGUAGE_WEIGHT };
-        for (final String dictType : DICT_TYPES_ORDERED_TO_GET_SUGGESTIONS) {
-            final Dictionary dictionary = dictionaryGroup.getDict(dictType);
-            if (null == dictionary) continue;
-            final ArrayList<SuggestedWordInfo> dictionarySuggestions =
-                    dictionary.getSuggestions(composer, prevWordsInfo, proximityInfo,
-                            settingsValuesForSuggestion, sessionId, languageWeight);
-            if (null == dictionarySuggestions) continue;
-            suggestionResults.addAll(dictionarySuggestions);
-            if (null != suggestionResults.mRawSuggestions) {
-                suggestionResults.mRawSuggestions.addAll(dictionarySuggestions);
+        for (final DictionaryGroup dictionaryGroup : dictionaryGroups) {
+            for (final String dictType : DICT_TYPES_ORDERED_TO_GET_SUGGESTIONS) {
+                final Dictionary dictionary = dictionaryGroup.getDict(dictType);
+                if (null == dictionary) continue;
+                final ArrayList<SuggestedWordInfo> dictionarySuggestions =
+                        dictionary.getSuggestions(composer, prevWordsInfo, proximityInfo,
+                                settingsValuesForSuggestion, sessionId, languageWeight);
+                if (null == dictionarySuggestions) continue;
+                suggestionResults.addAll(dictionarySuggestions);
+                if (null != suggestionResults.mRawSuggestions) {
+                    suggestionResults.mRawSuggestions.addAll(dictionarySuggestions);
+                }
             }
         }
         return suggestionResults;
@@ -559,20 +619,22 @@
         if (TextUtils.isEmpty(word)) {
             return false;
         }
-        final DictionaryGroup dictionaryGroup = mDictionaryGroup;
-        if (dictionaryGroup.mLocale == null) {
-            return false;
-        }
-        final String lowerCasedWord = word.toLowerCase(dictionaryGroup.mLocale);
-        for (final String dictType : DICT_TYPES_ORDERED_TO_GET_SUGGESTIONS) {
-            final Dictionary dictionary = dictionaryGroup.getDict(dictType);
-            // Ideally the passed map would come out of a {@link java.util.concurrent.Future} and
-            // would be immutable once it's finished initializing, but concretely a null test is
-            // probably good enough for the time being.
-            if (null == dictionary) continue;
-            if (dictionary.isValidWord(word)
-                    || (ignoreCase && dictionary.isValidWord(lowerCasedWord))) {
-                return true;
+        final DictionaryGroup[] dictionaryGroups = mDictionaryGroups;
+        for (final DictionaryGroup dictionaryGroup : dictionaryGroups) {
+            if (dictionaryGroup.mLocale == null) {
+                continue;
+            }
+            final String lowerCasedWord = word.toLowerCase(dictionaryGroup.mLocale);
+            for (final String dictType : DICT_TYPES_ORDERED_TO_GET_SUGGESTIONS) {
+                final Dictionary dictionary = dictionaryGroup.getDict(dictType);
+                // Ideally the passed map would come out of a {@link java.util.concurrent.Future} and
+                // would be immutable once it's finished initializing, but concretely a null test is
+                // probably good enough for the time being.
+                if (null == dictionary) continue;
+                if (dictionary.isValidWord(word)
+                        || (ignoreCase && dictionary.isValidWord(lowerCasedWord))) {
+                    return true;
+                }
             }
         }
         return false;
@@ -584,18 +646,20 @@
             return Dictionary.NOT_A_PROBABILITY;
         }
         int maxFreq = Dictionary.NOT_A_PROBABILITY;
-        final DictionaryGroup dictionaryGroup = mDictionaryGroup;
-        for (final String dictType : DICT_TYPES_ORDERED_TO_GET_SUGGESTIONS) {
-            final Dictionary dictionary = dictionaryGroup.getDict(dictType);
-            if (dictionary == null) continue;
-            final int tempFreq;
-            if (isGettingMaxFrequencyOfExactMatches) {
-                tempFreq = dictionary.getMaxFrequencyOfExactMatches(word);
-            } else {
-                tempFreq = dictionary.getFrequency(word);
-            }
-            if (tempFreq >= maxFreq) {
-                maxFreq = tempFreq;
+        final DictionaryGroup[] dictionaryGroups = mDictionaryGroups;
+        for (final DictionaryGroup dictionaryGroup : dictionaryGroups) {
+            for (final String dictType : DICT_TYPES_ORDERED_TO_GET_SUGGESTIONS) {
+                final Dictionary dictionary = dictionaryGroup.getDict(dictType);
+                if (dictionary == null) continue;
+                final int tempFreq;
+                if (isGettingMaxFrequencyOfExactMatches) {
+                    tempFreq = dictionary.getMaxFrequencyOfExactMatches(word);
+                } else {
+                    tempFreq = dictionary.getFrequency(word);
+                }
+                if (tempFreq >= maxFreq) {
+                    maxFreq = tempFreq;
+                }
             }
         }
         return maxFreq;
@@ -610,9 +674,12 @@
     }
 
     private void clearSubDictionary(final String dictName) {
-        final ExpandableBinaryDictionary dictionary = mDictionaryGroup.getSubDict(dictName);
-        if (dictionary != null) {
-            dictionary.clear();
+        final DictionaryGroup[] dictionaryGroups = mDictionaryGroups;
+        for (final DictionaryGroup dictionaryGroup : dictionaryGroups) {
+            final ExpandableBinaryDictionary dictionary = dictionaryGroup.getSubDict(dictName);
+            if (dictionary != null) {
+                dictionary.clear();
+            }
         }
     }
 
@@ -641,8 +708,10 @@
 
     public void addPhraseToContextualDictionary(final String[] phrase, final int probability,
             final int bigramProbabilityForWords, final int bigramProbabilityForPhrases) {
+        // TODO: we're inserting the phrase into the dictionary for the active language. Rethink
+        // this a bit from a theoretical point of view.
         final ExpandableBinaryDictionary contextualDict =
-                mDictionaryGroup.getSubDict(Dictionary.TYPE_CONTEXTUAL);
+                getDictionaryGroupForActiveLanguage().getSubDict(Dictionary.TYPE_CONTEXTUAL);
         if (contextualDict == null) {
             return;
         }
@@ -675,22 +744,27 @@
     }
 
     public void dumpDictionaryForDebug(final String dictName) {
-        final ExpandableBinaryDictionary dictToDump = mDictionaryGroup.getSubDict(dictName);
-        if (dictToDump == null) {
-            Log.e(TAG, "Cannot dump " + dictName + ". "
-                    + "The dictionary is not being used for suggestion or cannot be dumped.");
-            return;
+        final DictionaryGroup[] dictionaryGroups = mDictionaryGroups;
+        for (final DictionaryGroup dictionaryGroup : dictionaryGroups) {
+            final ExpandableBinaryDictionary dictToDump = dictionaryGroup.getSubDict(dictName);
+            if (dictToDump == null) {
+                Log.e(TAG, "Cannot dump " + dictName + ". "
+                        + "The dictionary is not being used for suggestion or cannot be dumped.");
+                return;
+            }
+            dictToDump.dumpAllWordsForDebug();
         }
-        dictToDump.dumpAllWordsForDebug();
     }
 
     public ArrayList<Pair<String, DictionaryStats>> getStatsOfEnabledSubDicts() {
         final ArrayList<Pair<String, DictionaryStats>> statsOfEnabledSubDicts = new ArrayList<>();
-        final DictionaryGroup dictionaryGroup = mDictionaryGroup;
-        for (final String dictType : SUB_DICT_TYPES) {
-            final ExpandableBinaryDictionary dictionary = dictionaryGroup.getSubDict(dictType);
-            if (dictionary == null) continue;
-            statsOfEnabledSubDicts.add(new Pair<>(dictType, dictionary.getDictionaryStats()));
+        final DictionaryGroup[] dictionaryGroups = mDictionaryGroups;
+        for (final DictionaryGroup dictionaryGroup : dictionaryGroups) {
+            for (final String dictType : SUB_DICT_TYPES) {
+                final ExpandableBinaryDictionary dictionary = dictionaryGroup.getSubDict(dictType);
+                if (dictionary == null) continue;
+                statsOfEnabledSubDicts.add(new Pair<>(dictType, dictionary.getDictionaryStats()));
+            }
         }
         return statsOfEnabledSubDicts;
     }
diff --git a/java/src/com/android/inputmethod/latin/DictionaryFacilitatorLruCache.java b/java/src/com/android/inputmethod/latin/DictionaryFacilitatorLruCache.java
index fa0265d..ff4a6bd 100644
--- a/java/src/com/android/inputmethod/latin/DictionaryFacilitatorLruCache.java
+++ b/java/src/com/android/inputmethod/latin/DictionaryFacilitatorLruCache.java
@@ -84,7 +84,7 @@
     private void waitForLoadingMainDictionary(final DictionaryFacilitator dictionaryFacilitator) {
         for (int i = 0; i < MAX_RETRY_COUNT_FOR_WAITING_FOR_LOADING_DICT; i++) {
             try {
-                dictionaryFacilitator.waitForLoadingMainDictionary(
+                dictionaryFacilitator.waitForLoadingMainDictionaries(
                         WAIT_FOR_LOADING_MAIN_DICT_IN_MILLISECONDS, TimeUnit.MILLISECONDS);
                 return;
             } catch (final InterruptedException e) {
diff --git a/java/src/com/android/inputmethod/latin/ExpandableBinaryDictionary.java b/java/src/com/android/inputmethod/latin/ExpandableBinaryDictionary.java
index a1dd67f..671ba67 100644
--- a/java/src/com/android/inputmethod/latin/ExpandableBinaryDictionary.java
+++ b/java/src/com/android/inputmethod/latin/ExpandableBinaryDictionary.java
@@ -156,23 +156,25 @@
     }
 
     private void asyncExecuteTaskWithWriteLock(final Runnable task) {
-        asyncExecuteTaskWithLock(mLock.writeLock(), task);
+        asyncExecuteTaskWithLock(mLock.writeLock(), mDictName /* executorName */, task);
     }
 
-    private void asyncExecuteTaskWithLock(final Lock lock, final Runnable task) {
-        asyncPreCheckAndExecuteTaskWithLock(lock, null /* preCheckTask */, task);
+    private void asyncExecuteTaskWithLock(final Lock lock, final String executorName,
+            final Runnable task) {
+        asyncPreCheckAndExecuteTaskWithLock(lock, null /* preCheckTask */, executorName, task);
     }
 
     private void asyncPreCheckAndExecuteTaskWithWriteLock(
             final Callable<Boolean> preCheckTask, final Runnable task) {
-        asyncPreCheckAndExecuteTaskWithLock(mLock.writeLock(), preCheckTask, task);
+        asyncPreCheckAndExecuteTaskWithLock(mLock.writeLock(), preCheckTask,
+                mDictName /* executorName */, task);
 
     }
 
     // Execute task with lock when the result of preCheckTask is true or preCheckTask is null.
     private void asyncPreCheckAndExecuteTaskWithLock(final Lock lock,
-            final Callable<Boolean> preCheckTask, final Runnable task) {
-        ExecutorUtils.getExecutor(mDictName).execute(new Runnable() {
+            final Callable<Boolean> preCheckTask, final String executorName, final Runnable task) {
+        ExecutorUtils.getExecutor(executorName).execute(new Runnable() {
             @Override
             public void run() {
                 if (preCheckTask != null) {
@@ -676,10 +678,10 @@
 
     public void dumpAllWordsForDebug() {
         reloadDictionaryIfRequired();
-        asyncExecuteTaskWithLock(mLock.readLock(), new Runnable() {
+        asyncExecuteTaskWithLock(mLock.readLock(), "dumpAllWordsForDebug", new Runnable() {
             @Override
             public void run() {
-                Log.d(TAG, "Dump dictionary: " + mDictName);
+                Log.d(TAG, "Dump dictionary: " + mDictName + " for " + mLocale);
                 try {
                     final DictionaryHeader header = mBinaryDictionary.getHeader();
                     Log.d(TAG, "Format version: " + mBinaryDictionary.getFormatVersion());
diff --git a/java/src/com/android/inputmethod/latin/LatinIME.java b/java/src/com/android/inputmethod/latin/LatinIME.java
index 0a64c4c..4757820 100644
--- a/java/src/com/android/inputmethod/latin/LatinIME.java
+++ b/java/src/com/android/inputmethod/latin/LatinIME.java
@@ -1000,7 +1000,7 @@
         mHandler.cancelUpdateSuggestionStrip();
 
         mainKeyboardView.setMainDictionaryAvailability(
-                mDictionaryFacilitator.hasInitializedMainDictionary());
+                mDictionaryFacilitator.hasAtLeastOneInitializedMainDictionary());
         mainKeyboardView.setKeyPreviewPopupEnabled(currentSettingsValues.mKeyPreviewPopupOn,
                 currentSettingsValues.mKeyPreviewPopupDismissDelay);
         mainKeyboardView.setSlidingKeyInputPreviewEnabled(
diff --git a/java/src/com/android/inputmethod/latin/PersonalizationHelperForDictionaryFacilitator.java b/java/src/com/android/inputmethod/latin/PersonalizationHelperForDictionaryFacilitator.java
index 43cebdf..396d062 100644
--- a/java/src/com/android/inputmethod/latin/PersonalizationHelperForDictionaryFacilitator.java
+++ b/java/src/com/android/inputmethod/latin/PersonalizationHelperForDictionaryFacilitator.java
@@ -88,17 +88,17 @@
 
     /**
      * Flush personalization dictionaries to dictionary files. Close dictionaries after writing
-     * files except the dictionary that is used for generating suggestions.
+     * files except the dictionaries that is used for generating suggestions.
      *
-     * @param personalizationDictUsedForSuggestion the personalization dictionary used for
+     * @param personalizationDictsUsedForSuggestion the personalization dictionaries used for
      * generating suggestions that won't be closed.
      */
     public void flushPersonalizationDictionariesToUpdate(
-            final ExpandableBinaryDictionary personalizationDictUsedForSuggestion) {
+            final HashSet<ExpandableBinaryDictionary> personalizationDictsUsedForSuggestion) {
         for (final ExpandableBinaryDictionary personalizationDict :
                 mPersonalizationDictsToUpdate.values()) {
             personalizationDict.asyncFlushBinaryDictionary();
-            if (personalizationDict != personalizationDictUsedForSuggestion) {
+            if (!personalizationDictsUsedForSuggestion.contains(personalizationDict)) {
                 // Close if the dictionary is not being used for suggestion.
                 personalizationDict.close();
             }
diff --git a/java/src/com/android/inputmethod/latin/Suggest.java b/java/src/com/android/inputmethod/latin/Suggest.java
index 9e4aa40..9bf0175 100644
--- a/java/src/com/android/inputmethod/latin/Suggest.java
+++ b/java/src/com/android/inputmethod/latin/Suggest.java
@@ -157,7 +157,7 @@
         if (!isCorrectionEnabled || !allowsToBeAutoCorrected || resultsArePredictions
                 || suggestionResults.isEmpty() || wordComposer.hasDigits()
                 || wordComposer.isMostlyCaps() || wordComposer.isResumed()
-                || !mDictionaryFacilitator.hasInitializedMainDictionary()
+                || !mDictionaryFacilitator.hasAtLeastOneInitializedMainDictionary()
                 || suggestionResults.first().isKindOf(SuggestedWordInfo.KIND_SHORTCUT)) {
             // If we don't have a main dictionary, we never want to auto-correct. The reason for
             // this is, the user may have a contact whose name happens to match a valid word in
diff --git a/java/src/com/android/inputmethod/latin/spellcheck/AndroidSpellCheckerService.java b/java/src/com/android/inputmethod/latin/spellcheck/AndroidSpellCheckerService.java
index 49b34d3..3523916 100644
--- a/java/src/com/android/inputmethod/latin/spellcheck/AndroidSpellCheckerService.java
+++ b/java/src/com/android/inputmethod/latin/spellcheck/AndroidSpellCheckerService.java
@@ -185,7 +185,7 @@
         try {
             final DictionaryFacilitator dictionaryFacilitator =
                     mDictionaryFacilitatorCache.get(locale);
-            return dictionaryFacilitator.hasInitializedMainDictionary();
+            return dictionaryFacilitator.hasAtLeastOneInitializedMainDictionary();
         } finally {
             mSemaphore.release();
         }
diff --git a/native/jni/src/suggest/core/dicnode/internal/dic_node_properties.h b/native/jni/src/suggest/core/dicnode/internal/dic_node_properties.h
index cecfc7a..1b796b5 100644
--- a/native/jni/src/suggest/core/dicnode/internal/dic_node_properties.h
+++ b/native/jni/src/suggest/core/dicnode/internal/dic_node_properties.h
@@ -32,7 +32,7 @@
  public:
     AK_FORCE_INLINE DicNodeProperties()
             : mChildrenPtNodeArrayPos(NOT_A_DICT_POS), mDicNodeCodePoint(NOT_A_CODE_POINT),
-              mWordId(NOT_A_WORD_ID), mDepth(0), mLeavingDepth(0) {}
+              mWordId(NOT_A_WORD_ID), mDepth(0), mLeavingDepth(0), mPrevWordCount(0) {}
 
     ~DicNodeProperties() {}
 
@@ -45,6 +45,7 @@
         mDepth = depth;
         mLeavingDepth = leavingDepth;
         prevWordIds.copyToArray(&mPrevWordIds, 0 /* offset */);
+        mPrevWordCount = prevWordIds.size();
     }
 
     // Init for root with prevWordsPtNodePos which is used for n-gram
@@ -55,6 +56,7 @@
         mDepth = 0;
         mLeavingDepth = 0;
         prevWordIds.copyToArray(&mPrevWordIds, 0 /* offset */);
+        mPrevWordCount = prevWordIds.size();
     }
 
     void initByCopy(const DicNodeProperties *const dicNodeProp) {
@@ -63,8 +65,9 @@
         mWordId = dicNodeProp->mWordId;
         mDepth = dicNodeProp->mDepth;
         mLeavingDepth = dicNodeProp->mLeavingDepth;
-        WordIdArrayView::fromArray(dicNodeProp->mPrevWordIds)
-                .copyToArray(&mPrevWordIds, 0 /* offset */);
+        const WordIdArrayView prevWordIdArrayView = dicNodeProp->getPrevWordIds();
+        prevWordIdArrayView.copyToArray(&mPrevWordIds, 0 /* offset */);
+        mPrevWordCount = prevWordIdArrayView.size();
     }
 
     // Init as passing child
@@ -74,8 +77,9 @@
         mWordId = dicNodeProp->mWordId;
         mDepth = dicNodeProp->mDepth + 1; // Increment the depth of a passing child
         mLeavingDepth = dicNodeProp->mLeavingDepth;
-        WordIdArrayView::fromArray(dicNodeProp->mPrevWordIds)
-                .copyToArray(&mPrevWordIds, 0 /* offset */);
+        const WordIdArrayView prevWordIdArrayView = dicNodeProp->getPrevWordIds();
+        prevWordIdArrayView.copyToArray(&mPrevWordIds, 0 /* offset */);
+        mPrevWordCount = prevWordIdArrayView.size();
     }
 
     int getChildrenPtNodeArrayPos() const {
@@ -104,7 +108,7 @@
     }
 
     const WordIdArrayView getPrevWordIds() const {
-        return WordIdArrayView::fromArray(mPrevWordIds);
+        return WordIdArrayView::fromArray(mPrevWordIds).limit(mPrevWordCount);
     }
 
     int getWordId() const {
@@ -121,6 +125,7 @@
     uint16_t mDepth;
     uint16_t mLeavingDepth;
     WordIdArray<MAX_PREV_WORD_COUNT_FOR_N_GRAM> mPrevWordIds;
+    size_t mPrevWordCount;
 };
 } // namespace latinime
 #endif // LATINIME_DIC_NODE_PROPERTIES_H
diff --git a/native/jni/src/suggest/policyimpl/dictionary/structure/v4/content/language_model_dict_content.cpp b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/content/language_model_dict_content.cpp
index f54bb15..0675de6 100644
--- a/native/jni/src/suggest/policyimpl/dictionary/structure/v4/content/language_model_dict_content.cpp
+++ b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/content/language_model_dict_content.cpp
@@ -39,7 +39,7 @@
 }
 
 int LanguageModelDictContent::getWordProbability(const WordIdArrayView prevWordIds,
-        const int wordId) const {
+        const int wordId, const HeaderPolicy *const headerPolicy) const {
     int bitmapEntryIndices[MAX_PREV_WORD_COUNT_FOR_N_GRAM + 1];
     bitmapEntryIndices[0] = mTrieMap.getRootBitmapEntryIndex();
     int maxLevel = 0;
@@ -58,14 +58,15 @@
         if (!result.mIsValid) {
             continue;
         }
-        const int probability =
-                ProbabilityEntry::decode(result.mValue, mHasHistoricalInfo).getProbability();
+        const ProbabilityEntry probabilityEntry =
+                ProbabilityEntry::decode(result.mValue, mHasHistoricalInfo);
         if (mHasHistoricalInfo) {
-            return std::min(
-                    probability + ForgettingCurveUtils::getProbabilityBiasForNgram(i + 1 /* n */),
-                    MAX_PROBABILITY);
+            const int probability = ForgettingCurveUtils::decodeProbability(
+                    probabilityEntry.getHistoricalInfo(), headerPolicy)
+                            + ForgettingCurveUtils::getProbabilityBiasForNgram(i + 1 /* n */);
+            return std::min(probability, MAX_PROBABILITY);
         } else {
-            return probability;
+            return probabilityEntry.getProbability();
         }
     }
     // Cannot find the word.
diff --git a/native/jni/src/suggest/policyimpl/dictionary/structure/v4/content/language_model_dict_content.h b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/content/language_model_dict_content.h
index 4e0b470..a793af4 100644
--- a/native/jni/src/suggest/policyimpl/dictionary/structure/v4/content/language_model_dict_content.h
+++ b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/content/language_model_dict_content.h
@@ -128,7 +128,8 @@
             const LanguageModelDictContent *const originalContent,
             int *const outNgramCount);
 
-    int getWordProbability(const WordIdArrayView prevWordIds, const int wordId) const;
+    int getWordProbability(const WordIdArrayView prevWordIds, const int wordId,
+            const HeaderPolicy *const headerPolicy) const;
 
     ProbabilityEntry getProbabilityEntry(const int wordId) const {
         return getNgramProbabilityEntry(WordIdArrayView(), wordId);
diff --git a/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_patricia_trie_policy.cpp b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_patricia_trie_policy.cpp
index e624bf3..d537711 100644
--- a/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_patricia_trie_policy.cpp
+++ b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_patricia_trie_policy.cpp
@@ -121,9 +121,10 @@
             mBuffers->getTerminalPositionLookupTable()->getTerminalPtNodePosition(wordId);
     const PtNodeParams ptNodeParams = mNodeReader.fetchPtNodeParamsInBufferFromPtNodePos(ptNodePos);
     // TODO: Support n-gram.
-    return WordAttributes(mBuffers->getLanguageModelDictContent()->getWordProbability(
-            prevWordIds.limit(1 /* maxSize */), wordId), ptNodeParams.isBlacklisted(),
-            ptNodeParams.isNotAWord(), ptNodeParams.getProbability() == 0);
+    const int probability = mBuffers->getLanguageModelDictContent()->getWordProbability(
+            prevWordIds.limit(1 /* maxSize */), wordId, mHeaderPolicy);
+    return WordAttributes(probability, ptNodeParams.isBlacklisted(), ptNodeParams.isNotAWord(),
+            probability == 0);
 }
 
 int Ver4PatriciaTriePolicy::getProbabilityOfWord(const WordIdArrayView prevWordIds,
@@ -309,30 +310,32 @@
     if (prevWordIds.empty()) {
         return false;
     }
-    // TODO: Support N-gram.
-    if (prevWordIds[0] == NOT_A_WORD_ID) {
-        if (prevWordsInfo->isNthPrevWordBeginningOfSentence(1 /* n */)) {
-            const std::vector<UnigramProperty::ShortcutProperty> shortcuts;
-            const UnigramProperty beginningOfSentenceUnigramProperty(
-                    true /* representsBeginningOfSentence */, true /* isNotAWord */,
-                    false /* isBlacklisted */, MAX_PROBABILITY /* probability */,
-                    NOT_A_TIMESTAMP /* timestamp */, 0 /* level */, 0 /* count */, &shortcuts);
-            if (!addUnigramEntry(prevWordsInfo->getNthPrevWordCodePoints(1 /* n */),
-                    &beginningOfSentenceUnigramProperty)) {
-                AKLOGE("Cannot add unigram entry for the beginning-of-sentence.");
-                return false;
-            }
-            // Refresh word ids.
-            prevWordsInfo->getPrevWordIds(this, &prevWordIdArray, false /* tryLowerCaseSearch */);
-        } else {
+    for (size_t i = 0; i < prevWordIds.size(); ++i) {
+        if (prevWordIds[i] != NOT_A_WORD_ID) {
+            continue;
+        }
+        if (!prevWordsInfo->isNthPrevWordBeginningOfSentence(i + 1 /* n */)) {
             return false;
         }
+        const std::vector<UnigramProperty::ShortcutProperty> shortcuts;
+        const UnigramProperty beginningOfSentenceUnigramProperty(
+                true /* representsBeginningOfSentence */, true /* isNotAWord */,
+                false /* isBlacklisted */, MAX_PROBABILITY /* probability */,
+                NOT_A_TIMESTAMP /* timestamp */, 0 /* level */, 0 /* count */, &shortcuts);
+        if (!addUnigramEntry(prevWordsInfo->getNthPrevWordCodePoints(1 /* n */),
+                &beginningOfSentenceUnigramProperty)) {
+            AKLOGE("Cannot add unigram entry for the beginning-of-sentence.");
+            return false;
+        }
+        // Refresh word ids.
+        prevWordsInfo->getPrevWordIds(this, &prevWordIdArray, false /* tryLowerCaseSearch */);
     }
     const int wordId = getWordId(CodePointArrayView(*bigramProperty->getTargetCodePoints()),
             false /* forceLowerCaseSearch */);
     if (wordId == NOT_A_WORD_ID) {
         return false;
     }
+    // TODO: Support N-gram.
     bool addedNewEntry = false;
     WordIdArray<MAX_PREV_WORD_COUNT_FOR_N_GRAM> prevWordsPtNodePos;
     for (size_t i = 0; i < prevWordsPtNodePos.size(); ++i) {
@@ -374,8 +377,7 @@
     WordIdArray<MAX_PREV_WORD_COUNT_FOR_N_GRAM> prevWordIdArray;
     const WordIdArrayView prevWordIds = prevWordsInfo->getPrevWordIds(this, &prevWordIdArray,
             false /* tryLowerCaseSerch */);
-    // TODO: Support N-gram.
-    if (prevWordIds.empty() || prevWordIds[0] == NOT_A_WORD_ID) {
+    if (prevWordIds.empty() || prevWordIds.contains(NOT_A_WORD_ID)) {
         return false;
     }
     const int wordId = getWordId(wordCodePoints, false /* forceLowerCaseSearch */);
diff --git a/native/jni/src/utils/int_array_view.h b/native/jni/src/utils/int_array_view.h
index caa13d9..cc5f328 100644
--- a/native/jni/src/utils/int_array_view.h
+++ b/native/jni/src/utils/int_array_view.h
@@ -17,6 +17,7 @@
 #ifndef LATINIME_INT_ARRAY_VIEW_H
 #define LATINIME_INT_ARRAY_VIEW_H
 
+#include <algorithm>
 #include <array>
 #include <cstdint>
 #include <cstring>
@@ -92,12 +93,16 @@
         return mPtr + mSize;
     }
 
+    AK_FORCE_INLINE bool contains(const int value) const {
+        return std::find(begin(), end(), value) != end();
+    }
+
     // Returns the view whose size is smaller than or equal to the given count.
-    const IntArrayView limit(const size_t maxSize) const {
+    AK_FORCE_INLINE const IntArrayView limit(const size_t maxSize) const {
         return IntArrayView(mPtr, std::min(maxSize, mSize));
     }
 
-    const IntArrayView skip(const size_t n) const {
+    AK_FORCE_INLINE const IntArrayView skip(const size_t n) const {
         if (mSize <= n) {
             return IntArrayView();
         }
diff --git a/native/jni/tests/suggest/policyimpl/dictionary/structure/v4/content/language_model_dict_content_test.cpp b/native/jni/tests/suggest/policyimpl/dictionary/structure/v4/content/language_model_dict_content_test.cpp
index 7608b45..c5849d0 100644
--- a/native/jni/tests/suggest/policyimpl/dictionary/structure/v4/content/language_model_dict_content_test.cpp
+++ b/native/jni/tests/suggest/policyimpl/dictionary/structure/v4/content/language_model_dict_content_test.cpp
@@ -107,13 +107,15 @@
     languageModelDictContent.setProbabilityEntry(prevWordIds[0], &probabilityEntry);
     languageModelDictContent.setNgramProbabilityEntry(prevWordIds.limit(1), wordId,
             &bigramProbabilityEntry);
-    EXPECT_EQ(bigramProbability, languageModelDictContent.getWordProbability(prevWordIds, wordId));
+    EXPECT_EQ(bigramProbability, languageModelDictContent.getWordProbability(prevWordIds, wordId,
+            nullptr /* headerPolicy */));
     const ProbabilityEntry trigramProbabilityEntry(flag, trigramProbability);
     languageModelDictContent.setNgramProbabilityEntry(prevWordIds.limit(1),
             prevWordIds[1], &probabilityEntry);
     languageModelDictContent.setNgramProbabilityEntry(prevWordIds.limit(2), wordId,
             &trigramProbabilityEntry);
-    EXPECT_EQ(trigramProbability, languageModelDictContent.getWordProbability(prevWordIds, wordId));
+    EXPECT_EQ(trigramProbability, languageModelDictContent.getWordProbability(prevWordIds, wordId,
+            nullptr /* headerPolicy */));
 }
 
 }  // namespace
diff --git a/native/jni/tests/utils/int_array_view_test.cpp b/native/jni/tests/utils/int_array_view_test.cpp
index 3bc294c..934e27e 100644
--- a/native/jni/tests/utils/int_array_view_test.cpp
+++ b/native/jni/tests/utils/int_array_view_test.cpp
@@ -58,6 +58,19 @@
     EXPECT_EQ(object, intArrayView[0]);
 }
 
+TEST(IntArrayViewTest, TestContains) {
+    EXPECT_FALSE(IntArrayView().contains(0));
+    EXPECT_FALSE(IntArrayView().contains(1));
+
+    const std::vector<int> intVector = {3, 2, 1, 0, -1, -2};
+    IntArrayView intArrayView(intVector);
+    EXPECT_TRUE(intArrayView.contains(0));
+    EXPECT_TRUE(intArrayView.contains(3));
+    EXPECT_TRUE(intArrayView.contains(-2));
+    EXPECT_FALSE(intArrayView.contains(-3));
+    EXPECT_FALSE(intArrayView.limit(0).contains(3));
+}
+
 TEST(IntArrayViewTest, TestLimit) {
     const std::vector<int> intVector = {3, 2, 1, 0, -1, -2};
     IntArrayView intArrayView(intVector);
diff --git a/tests/AndroidManifest.xml b/tests/AndroidManifest.xml
index 4ca846b..8a628cd 100644
--- a/tests/AndroidManifest.xml
+++ b/tests/AndroidManifest.xml
@@ -17,7 +17,7 @@
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
     package="com.android.inputmethod.latin.tests">
 
-    <uses-sdk android:minSdkVersion="14" android:targetSdkVersion="19" />
+    <uses-sdk android:minSdkVersion="14" android:targetSdkVersion="21" />
 
     <uses-permission android:name="android.permission.READ_CONTACTS" />