diff --git a/java/src/com/android/inputmethod/latin/BinaryDictionary.java b/java/src/com/android/inputmethod/latin/BinaryDictionary.java
index a351ee9..b88509f 100644
--- a/java/src/com/android/inputmethod/latin/BinaryDictionary.java
+++ b/java/src/com/android/inputmethod/latin/BinaryDictionary.java
@@ -41,6 +41,7 @@
 import java.util.Arrays;
 import java.util.HashMap;
 import java.util.Locale;
+import java.util.Map;
 
 /**
  * Implements a static, compacted, binary dictionary of standard words.
@@ -123,8 +124,7 @@
     }
 
     /**
-     * Constructor for the binary dictionary. This is supposed to be called from the
-     * dictionary factory.
+     * Constructs binary dictionary using existing dictionary file.
      * @param filename the name of the file to read through native code.
      * @param offset the offset of the dictionary data within the file.
      * @param length the length of the binary data.
@@ -145,6 +145,38 @@
         loadDictionary(filename, offset, length, isUpdatable);
     }
 
+    /**
+     * Constructs binary dictionary on memory.
+     * @param filename the name of the file used to flush.
+     * @param useFullEditDistance whether to use the full edit distance in suggestions
+     * @param dictType the dictionary type, as a human-readable string
+     * @param formatVersion the format version of the dictionary
+     * @param attributeMap the attributes of the dictionary
+     */
+    @UsedForTesting
+    public BinaryDictionary(final String filename, final boolean useFullEditDistance,
+            final Locale locale, final String dictType, final long formatVersion,
+            final Map<String, String> attributeMap) {
+        super(dictType);
+        mLocale = locale;
+        mDictSize = 0;
+        mDictFilePath = filename;
+        // On memory dictionary is always updatable.
+        mIsUpdatable = true;
+        mHasUpdated = false;
+        mNativeSuggestOptions.setUseFullEditDistance(useFullEditDistance);
+        final String[] keyArray = new String[attributeMap.size()];
+        final String[] valueArray = new String[attributeMap.size()];
+        int index = 0;
+        for (final String key : attributeMap.keySet()) {
+            keyArray[index] = key;
+            valueArray[index] = attributeMap.get(key);
+            index++;
+        }
+        mNativeDict = createOnMemoryNative(formatVersion, locale.toString(), keyArray, valueArray);
+    }
+
+
     static {
         JniUtils.loadNativeLibrary();
     }
diff --git a/native/jni/src/suggest/policyimpl/dictionary/header/header_policy.h b/native/jni/src/suggest/policyimpl/dictionary/header/header_policy.h
index ab943a3..251a719 100644
--- a/native/jni/src/suggest/policyimpl/dictionary/header/header_policy.h
+++ b/native/jni/src/suggest/policyimpl/dictionary/header/header_policy.h
@@ -99,6 +99,27 @@
               mMaxBigramCount(HeaderReadWriteUtils::readIntAttributeValue(
                       &mAttributeMap, MAX_BIGRAM_COUNT_KEY, DEFAULT_MAX_BIGRAM_COUNT)) {}
 
+    // Copy header information
+    HeaderPolicy(const HeaderPolicy *const headerPolicy)
+            : mDictFormatVersion(headerPolicy->mDictFormatVersion),
+              mDictionaryFlags(headerPolicy->mDictionaryFlags), mSize(headerPolicy->mSize),
+              mAttributeMap(headerPolicy->mAttributeMap), mLocale(headerPolicy->mLocale),
+              mMultiWordCostMultiplier(headerPolicy->mMultiWordCostMultiplier),
+              mRequiresGermanUmlautProcessing(headerPolicy->mRequiresGermanUmlautProcessing),
+              mIsDecayingDict(headerPolicy->mIsDecayingDict),
+              mDate(headerPolicy->mDate), mLastDecayedTime(headerPolicy->mLastDecayedTime),
+              mUnigramCount(headerPolicy->mUnigramCount), mBigramCount(headerPolicy->mBigramCount),
+              mExtendedRegionSize(headerPolicy->mExtendedRegionSize),
+              mHasHistoricalInfoOfWords(headerPolicy->mHasHistoricalInfoOfWords),
+              mForgettingCurveOccurrencesToLevelUp(
+                      headerPolicy->mForgettingCurveOccurrencesToLevelUp),
+              mForgettingCurveProbabilityValuesTableId(
+                      headerPolicy->mForgettingCurveProbabilityValuesTableId),
+              mForgettingCurveDurationToLevelDown(
+                      headerPolicy->mForgettingCurveDurationToLevelDown),
+              mMaxUnigramCount(headerPolicy->mMaxUnigramCount),
+              mMaxBigramCount(headerPolicy->mMaxBigramCount) {}
+
     // Temporary dummy header.
     HeaderPolicy()
             : mDictFormatVersion(FormatUtils::UNKNOWN_VERSION), mDictionaryFlags(0), mSize(0),
diff --git a/native/jni/src/suggest/policyimpl/dictionary/structure/dictionary_structure_with_buffer_policy_factory.cpp b/native/jni/src/suggest/policyimpl/dictionary/structure/dictionary_structure_with_buffer_policy_factory.cpp
index eefedc3..be7e43b 100644
--- a/native/jni/src/suggest/policyimpl/dictionary/structure/dictionary_structure_with_buffer_policy_factory.cpp
+++ b/native/jni/src/suggest/policyimpl/dictionary/structure/dictionary_structure_with_buffer_policy_factory.cpp
@@ -19,10 +19,12 @@
 #include <climits>
 
 #include "defines.h"
+#include "suggest/policyimpl/dictionary/structure/pt_common/dynamic_pt_writing_utils.h"
 #include "suggest/policyimpl/dictionary/structure/v2/patricia_trie_policy.h"
 #include "suggest/policyimpl/dictionary/structure/v4/ver4_dict_buffers.h"
 #include "suggest/policyimpl/dictionary/structure/v4/ver4_dict_constants.h"
 #include "suggest/policyimpl/dictionary/structure/v4/ver4_patricia_trie_policy.h"
+#include "suggest/policyimpl/dictionary/utils/dict_file_writing_utils.h"
 #include "suggest/policyimpl/dictionary/utils/file_utils.h"
 #include "suggest/policyimpl/dictionary/utils/format_utils.h"
 #include "suggest/policyimpl/dictionary/utils/mmapped_buffer.h"
@@ -56,6 +58,11 @@
             Ver4DictBuffers::Ver4DictBuffersPtr dictBuffers =
                     Ver4DictBuffers::createVer4DictBuffers(&headerPolicy,
                             Ver4DictConstants::MAX_DICT_EXTENDED_REGION_SIZE);
+            if (!DynamicPtWritingUtils::writeEmptyDictionary(
+                    dictBuffers->getWritableTrieBuffer(), 0 /* rootPos */)) {
+                AKLOGE("Empty ver4 dictionary structure cannot be created on memory.");
+                return DictionaryStructureWithBufferPolicy::StructurePolicyPtr(nullptr);
+            }
             return DictionaryStructureWithBufferPolicy::StructurePolicyPtr(
                     new Ver4PatriciaTriePolicy(std::move(dictBuffers)));
         }
diff --git a/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_dict_buffers.cpp b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_dict_buffers.cpp
index eda882d..95f6544 100644
--- a/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_dict_buffers.cpp
+++ b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_dict_buffers.cpp
@@ -131,7 +131,7 @@
           mIsUpdatable(isUpdatable) {}
 
 Ver4DictBuffers::Ver4DictBuffers(const HeaderPolicy *const headerPolicy, const int maxTrieSize)
-        : mHeaderBuffer(nullptr), mDictBuffer(nullptr), mHeaderPolicy(),
+        : mHeaderBuffer(nullptr), mDictBuffer(nullptr), mHeaderPolicy(headerPolicy),
           mExpandableHeaderBuffer(Ver4DictConstants::MAX_DICTIONARY_SIZE),
           mExpandableTrieBuffer(maxTrieSize), mTerminalPositionLookupTable(),
           mProbabilityDictContent(headerPolicy->hasHistoricalInfoOfWords()),
diff --git a/tests/src/com/android/inputmethod/latin/BinaryDictionaryTests.java b/tests/src/com/android/inputmethod/latin/BinaryDictionaryTests.java
index b476627..0fb0fa5 100644
--- a/tests/src/com/android/inputmethod/latin/BinaryDictionaryTests.java
+++ b/tests/src/com/android/inputmethod/latin/BinaryDictionaryTests.java
@@ -97,6 +97,37 @@
         binaryDictionary.close();
     }
 
+    public void testConstructingDictionaryOnMemory() {
+        testConstructingDictionaryOnMemory(FormatSpec.VERSION4);
+    }
+
+    private void testConstructingDictionaryOnMemory(final int formatVersion) {
+        File dictFile = null;
+        try {
+            dictFile = createEmptyDictionaryAndGetFile("TestBinaryDictionary", formatVersion);
+        } catch (IOException e) {
+            fail("IOException while writing an initial dictionary : " + e);
+        }
+        FileUtils.deleteRecursively(dictFile);
+        assertFalse(dictFile.exists());
+        BinaryDictionary binaryDictionary = new BinaryDictionary(dictFile.getAbsolutePath(),
+                true /* useFullEditDistance */, Locale.getDefault(), TEST_LOCALE, formatVersion,
+                new HashMap<String, String>());
+        assertTrue(binaryDictionary.isValidDictionary());
+        assertEquals(formatVersion, binaryDictionary.getFormatVersion());
+        final int probability = 100;
+        addUnigramWord(binaryDictionary, "word", probability);
+        assertEquals(probability, binaryDictionary.getFrequency("word"));
+        assertFalse(dictFile.exists());
+        binaryDictionary.flush();
+        assertTrue(dictFile.exists());
+        assertTrue(binaryDictionary.isValidDictionary());
+        assertEquals(formatVersion, binaryDictionary.getFormatVersion());
+        assertEquals(probability, binaryDictionary.getFrequency("word"));
+        binaryDictionary.close();
+        dictFile.delete();
+    }
+
     public void testAddTooLongWord() {
         testAddTooLongWord(FormatSpec.VERSION4);
     }