diff --git a/java/src/com/android/inputmethod/latin/makedict/BinaryDictDecoderUtils.java b/java/src/com/android/inputmethod/latin/makedict/BinaryDictDecoderUtils.java
index fc5788d..845299c 100644
--- a/java/src/com/android/inputmethod/latin/makedict/BinaryDictDecoderUtils.java
+++ b/java/src/com/android/inputmethod/latin/makedict/BinaryDictDecoderUtils.java
@@ -500,16 +500,14 @@
      * Reads a buffer and returns the memory representation of the dictionary.
      *
      * This high-level method takes a buffer and reads its contents, populating a
-     * FusionDictionary structure. The optional dict argument is an existing dictionary to
-     * which words from the buffer should be added. If it is null, a new dictionary is created.
+     * FusionDictionary structure.
      *
      * @param dictDecoder the dict decoder.
-     * @param dict an optional dictionary to add words to, or null.
-     * @return the created (or merged) dictionary.
+     * @return the created dictionary.
      */
     @UsedForTesting
-    /* package */ static FusionDictionary readDictionaryBinary(final DictDecoder dictDecoder,
-            final FusionDictionary dict) throws IOException, UnsupportedFormatException {
+    /* package */ static FusionDictionary readDictionaryBinary(final DictDecoder dictDecoder)
+            throws IOException, UnsupportedFormatException {
         // Read header
         final DictionaryHeader fileHeader = dictDecoder.readHeader();
 
@@ -517,29 +515,7 @@
         Map<Integer, PtNode> reversePtNodeMapping = new TreeMap<Integer, PtNode>();
         final PtNodeArray root = readNodeArray(dictDecoder, fileHeader.mBodyOffset,
                 reverseNodeArrayMapping, reversePtNodeMapping, fileHeader.mFormatOptions);
-
-        FusionDictionary newDict = new FusionDictionary(root, fileHeader.mDictionaryOptions);
-        if (null != dict) {
-            for (final WordProperty wordProperty : dict) {
-                if (wordProperty.mIsBlacklistEntry) {
-                    newDict.addBlacklistEntry(wordProperty.mWord, wordProperty.mShortcutTargets,
-                            wordProperty.mIsNotAWord);
-                } else {
-                    newDict.add(wordProperty.mWord, wordProperty.mProbabilityInfo,
-                            wordProperty.mShortcutTargets, wordProperty.mIsNotAWord);
-                }
-            }
-            for (final WordProperty wordProperty : dict) {
-                // By construction a binary dictionary may not have bigrams pointing to
-                // words that are not also registered as unigrams so we don't have to avoid
-                // them explicitly here.
-                for (final WeightedString bigram : wordProperty.mBigrams) {
-                    newDict.setBigram(wordProperty.mWord, bigram.mWord, bigram.mProbabilityInfo);
-                }
-            }
-        }
-
-        return newDict;
+        return new FusionDictionary(root, fileHeader.mDictionaryOptions);
     }
 
     /**
diff --git a/java/src/com/android/inputmethod/latin/makedict/DictDecoder.java b/java/src/com/android/inputmethod/latin/makedict/DictDecoder.java
index a93a8bb..0fb98ab 100644
--- a/java/src/com/android/inputmethod/latin/makedict/DictDecoder.java
+++ b/java/src/com/android/inputmethod/latin/makedict/DictDecoder.java
@@ -54,18 +54,15 @@
      * Reads a buffer and returns the memory representation of the dictionary.
      *
      * This high-level method takes a buffer and reads its contents, populating a
-     * FusionDictionary structure. The optional dict argument is an existing dictionary to
-     * which words from the buffer should be added. If it is null, a new dictionary is created.
+     * FusionDictionary structure.
      *
-     * @param dict an optional dictionary to add words to, or null.
      * @param deleteDictIfBroken a flag indicating whether this method should remove the broken
      * dictionary or not.
-     * @return the created (or merged) dictionary.
+     * @return the created dictionary.
      */
     @UsedForTesting
-    public FusionDictionary readDictionaryBinary(final FusionDictionary dict,
-            final boolean deleteDictIfBroken)
-                    throws FileNotFoundException, IOException, UnsupportedFormatException;
+    public FusionDictionary readDictionaryBinary(final boolean deleteDictIfBroken)
+            throws FileNotFoundException, IOException, UnsupportedFormatException;
 
     /**
      * Gets the address of the last PtNode of the exact matching word in the dictionary.
diff --git a/java/src/com/android/inputmethod/latin/makedict/Ver2DictDecoder.java b/java/src/com/android/inputmethod/latin/makedict/Ver2DictDecoder.java
index fd6138d..5dda715 100644
--- a/java/src/com/android/inputmethod/latin/makedict/Ver2DictDecoder.java
+++ b/java/src/com/android/inputmethod/latin/makedict/Ver2DictDecoder.java
@@ -236,14 +236,13 @@
     }
 
     @Override
-    public FusionDictionary readDictionaryBinary(final FusionDictionary dict,
-            final boolean deleteDictIfBroken)
+    public FusionDictionary readDictionaryBinary(final boolean deleteDictIfBroken)
             throws FileNotFoundException, IOException, UnsupportedFormatException {
         if (mDictBuffer == null) {
             openDictBuffer();
         }
         try {
-            return BinaryDictDecoderUtils.readDictionaryBinary(this, dict);
+            return BinaryDictDecoderUtils.readDictionaryBinary(this);
         } catch (IOException e) {
             Log.e(TAG, "The dictionary " + mDictionaryBinaryFile.getName() + " is broken.", e);
             if (deleteDictIfBroken && !mDictionaryBinaryFile.delete()) {
diff --git a/java/src/com/android/inputmethod/latin/makedict/Ver4DictDecoder.java b/java/src/com/android/inputmethod/latin/makedict/Ver4DictDecoder.java
index 1c74852..abaf966 100644
--- a/java/src/com/android/inputmethod/latin/makedict/Ver4DictDecoder.java
+++ b/java/src/com/android/inputmethod/latin/makedict/Ver4DictDecoder.java
@@ -56,11 +56,10 @@
     }
 
     @Override
-    public FusionDictionary readDictionaryBinary(final FusionDictionary dict,
-            final boolean deleteDictIfBroken)
+    public FusionDictionary readDictionaryBinary(final boolean deleteDictIfBroken)
             throws FileNotFoundException, IOException, UnsupportedFormatException {
         final DictionaryHeader header = readHeader();
-        final FusionDictionary fusionDict = dict != null ? dict :
+        final FusionDictionary fusionDict =
                 new FusionDictionary(new FusionDictionary.PtNodeArray(), header.mDictionaryOptions);
         int token = 0;
         final ArrayList<WordProperty> wordProperties = CollectionUtils.newArrayList();
diff --git a/tests/src/com/android/inputmethod/latin/BinaryDictionaryDecayingTests.java b/tests/src/com/android/inputmethod/latin/BinaryDictionaryDecayingTests.java
index 7d664c8..64b793e 100644
--- a/tests/src/com/android/inputmethod/latin/BinaryDictionaryDecayingTests.java
+++ b/tests/src/com/android/inputmethod/latin/BinaryDictionaryDecayingTests.java
@@ -152,8 +152,8 @@
 
         final DictDecoder dictDecoder = FormatSpec.getDictDecoder(dictFile);
         try {
-            final FusionDictionary dict = dictDecoder.readDictionaryBinary(null,
-                    false /* deleteDictIfBroken */);
+            final FusionDictionary dict =
+                    dictDecoder.readDictionaryBinary(false /* deleteDictIfBroken */);
             PtNode ptNode = FusionDictionary.findWordInTree(dict.mRootNodeArray, "a");
             assertNotNull(ptNode);
             assertTrue(ptNode.isTerminal());
diff --git a/tests/src/com/android/inputmethod/latin/makedict/BinaryDictDecoderEncoderTests.java b/tests/src/com/android/inputmethod/latin/makedict/BinaryDictDecoderEncoderTests.java
index 86f2458..4fb0636 100644
--- a/tests/src/com/android/inputmethod/latin/makedict/BinaryDictDecoderEncoderTests.java
+++ b/tests/src/com/android/inputmethod/latin/makedict/BinaryDictDecoderEncoderTests.java
@@ -252,7 +252,7 @@
         try {
             final DictDecoder dictDecoder = FormatSpec.getDictDecoder(file, bufferType);
             now = System.currentTimeMillis();
-            dict = dictDecoder.readDictionaryBinary(null, false /* deleteDictIfBroken */);
+            dict = dictDecoder.readDictionaryBinary(false /* deleteDictIfBroken */);
             diff  = System.currentTimeMillis() - now;
         } catch (IOException e) {
             Log.e(TAG, "IOException while reading dictionary", e);
diff --git a/tools/dicttool/src/com/android/inputmethod/latin/dicttool/BinaryDictOffdeviceUtils.java b/tools/dicttool/src/com/android/inputmethod/latin/dicttool/BinaryDictOffdeviceUtils.java
index e571bc2..d1df81b 100644
--- a/tools/dicttool/src/com/android/inputmethod/latin/dicttool/BinaryDictOffdeviceUtils.java
+++ b/tools/dicttool/src/com/android/inputmethod/latin/dicttool/BinaryDictOffdeviceUtils.java
@@ -198,7 +198,7 @@
                         System.out.println("Packaging : " + decodedSpec.describeChain());
                         System.out.println("Uncompressed size : " + decodedSpec.mFile.length());
                     }
-                    return dictDecoder.readDictionaryBinary(null, false /* deleteDictIfBroken */);
+                    return dictDecoder.readDictionaryBinary(false /* deleteDictIfBroken */);
                 }
             }
         } catch (IOException e) {
diff --git a/tools/dicttool/src/com/android/inputmethod/latin/dicttool/DictionaryMaker.java b/tools/dicttool/src/com/android/inputmethod/latin/dicttool/DictionaryMaker.java
index 143bce5..80d71fc 100644
--- a/tools/dicttool/src/com/android/inputmethod/latin/dicttool/DictionaryMaker.java
+++ b/tools/dicttool/src/com/android/inputmethod/latin/dicttool/DictionaryMaker.java
@@ -265,7 +265,7 @@
             throws FileNotFoundException, IOException, UnsupportedFormatException {
         final File file = new File(binaryFilename);
         final DictDecoder dictDecoder = FormatSpec.getDictDecoder(file);
-        return dictDecoder.readDictionaryBinary(null, false /* deleteDictIfBroken */);
+        return dictDecoder.readDictionaryBinary(false /* deleteDictIfBroken */);
     }
 
     /**
diff --git a/tools/dicttool/tests/com/android/inputmethod/latin/dicttool/BinaryDictOffdeviceUtilsTests.java b/tools/dicttool/tests/com/android/inputmethod/latin/dicttool/BinaryDictOffdeviceUtilsTests.java
index 69b49f0..7a4f6f7 100644
--- a/tools/dicttool/tests/com/android/inputmethod/latin/dicttool/BinaryDictOffdeviceUtilsTests.java
+++ b/tools/dicttool/tests/com/android/inputmethod/latin/dicttool/BinaryDictOffdeviceUtilsTests.java
@@ -78,9 +78,8 @@
         }
         assertEquals("Wrong decode spec", 3, decodeSpec.mDecoderSpec.size());
         final DictDecoder dictDecoder = FormatSpec.getDictDecoder(decodeSpec.mFile);
-        final FusionDictionary resultDict = dictDecoder.readDictionaryBinary(
-                null /* dict : an optional dictionary to add words to, or null */,
-                false /* deleteDictIfBroken */);
+        final FusionDictionary resultDict =
+                dictDecoder.readDictionaryBinary(false /* deleteDictIfBroken */);
         assertEquals("Wrong version attribute", VERSION, resultDict.mOptions.mAttributes.get(
                 DictionaryHeader.DICTIONARY_VERSION_KEY));
         assertEquals("Wrong locale attribute", LOCALE, resultDict.mOptions.mAttributes.get(