diff --git a/java/src/com/android/inputmethod/latin/makedict/DictUpdater.java b/java/src/com/android/inputmethod/latin/makedict/DictUpdater.java
index 709ea33..c4f7ec9 100644
--- a/java/src/com/android/inputmethod/latin/makedict/DictUpdater.java
+++ b/java/src/com/android/inputmethod/latin/makedict/DictUpdater.java
@@ -16,6 +16,7 @@
 
 package com.android.inputmethod.latin.makedict;
 
+import com.android.inputmethod.annotations.UsedForTesting;
 import com.android.inputmethod.latin.makedict.FusionDictionary.WeightedString;
 
 import java.io.IOException;
@@ -24,6 +25,7 @@
 /**
  * An interface of a binary dictionary updater.
  */
+@UsedForTesting
 public interface DictUpdater extends DictDecoder {
 
     /**
@@ -31,6 +33,7 @@
      *
      * @param word the word to be deleted.
      */
+    @UsedForTesting
     public void deleteWord(final String word) throws IOException, UnsupportedFormatException;
 
     /**
@@ -43,6 +46,7 @@
      * @param isBlackListEntry whether this should be a blacklist entry.
      */
     // TODO: Support batch insertion.
+    @UsedForTesting
     public void insertWord(final String word, final int frequency,
             final ArrayList<WeightedString> bigramStrings,
             final ArrayList<WeightedString> shortcuts, final boolean isNotAWord,
diff --git a/java/src/com/android/inputmethod/latin/makedict/Ver3DictUpdater.java b/java/src/com/android/inputmethod/latin/makedict/Ver3DictUpdater.java
index fa7ae31..07adda6 100644
--- a/java/src/com/android/inputmethod/latin/makedict/Ver3DictUpdater.java
+++ b/java/src/com/android/inputmethod/latin/makedict/Ver3DictUpdater.java
@@ -57,7 +57,7 @@
     public void deleteWord(final String word) throws IOException, UnsupportedFormatException {
         if (mOutStream == null) openStreamAndBuffer();
         mDictBuffer.position(0);
-        super.readHeader();
+        readHeader();
         final int wordPos = getTerminalPosition(word);
         if (wordPos != FormatSpec.NOT_VALID_WORD) {
             mDictBuffer.position(wordPos);
diff --git a/java/src/com/android/inputmethod/latin/makedict/Ver4DictDecoder.java b/java/src/com/android/inputmethod/latin/makedict/Ver4DictDecoder.java
index bab24e3..5372907 100644
--- a/java/src/com/android/inputmethod/latin/makedict/Ver4DictDecoder.java
+++ b/java/src/com/android/inputmethod/latin/makedict/Ver4DictDecoder.java
@@ -48,7 +48,7 @@
 
     private final File mDictDirectory;
     private final DictionaryBufferFactory mBufferFactory;
-    private DictBuffer mDictBuffer;
+    protected DictBuffer mDictBuffer;
     private DictBuffer mFrequencyBuffer;
     private DictBuffer mTerminalAddressTableBuffer;
     private DictBuffer mBigramBuffer;
diff --git a/java/src/com/android/inputmethod/latin/makedict/Ver4DictUpdater.java b/java/src/com/android/inputmethod/latin/makedict/Ver4DictUpdater.java
new file mode 100644
index 0000000..3d8f186
--- /dev/null
+++ b/java/src/com/android/inputmethod/latin/makedict/Ver4DictUpdater.java
@@ -0,0 +1,59 @@
+/*
+ * Copyright (C) 2013 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.android.inputmethod.latin.makedict;
+
+import com.android.inputmethod.annotations.UsedForTesting;
+import com.android.inputmethod.latin.makedict.FusionDictionary.WeightedString;
+
+import java.io.File;
+import java.io.IOException;
+import java.util.ArrayList;
+
+/**
+ * An implementation of DictUpdater for version 4 binary dictionary.
+ */
+@UsedForTesting
+public class Ver4DictUpdater extends Ver4DictDecoder implements DictUpdater {
+
+    @UsedForTesting
+    public Ver4DictUpdater(final File dictDirectory, final int factoryType) {
+        // DictUpdater must have an updatable DictBuffer.
+        super(dictDirectory, ((factoryType & MASK_DICTBUFFER) == USE_BYTEARRAY)
+                ? USE_BYTEARRAY : USE_WRITABLE_BYTEBUFFER);
+    }
+
+    @Override
+    public void deleteWord(final String word) throws IOException, UnsupportedFormatException {
+        if (mDictBuffer == null) openDictBuffer();
+        readHeader();
+        final int wordPos = getTerminalPosition(word);
+        if (wordPos != FormatSpec.NOT_VALID_WORD) {
+            mDictBuffer.position(wordPos);
+            final int flags = PtNodeReader.readPtNodeOptionFlags(mDictBuffer);
+            mDictBuffer.position(wordPos);
+            mDictBuffer.put((byte) DynamicBinaryDictIOUtils.markAsDeleted(flags));
+        }
+    }
+
+    @Override
+    public void insertWord(final String word, final int frequency,
+        final ArrayList<WeightedString> bigramStrings, final ArrayList<WeightedString> shortcuts,
+        final boolean isNotAWord, final boolean isBlackListEntry)
+                throws IOException, UnsupportedFormatException {
+        // TODO: Implement this method.
+    }
+}
diff --git a/tests/src/com/android/inputmethod/latin/makedict/BinaryDictDecoderEncoderTests.java b/tests/src/com/android/inputmethod/latin/makedict/BinaryDictDecoderEncoderTests.java
index aa16583..0189b33 100644
--- a/tests/src/com/android/inputmethod/latin/makedict/BinaryDictDecoderEncoderTests.java
+++ b/tests/src/com/android/inputmethod/latin/makedict/BinaryDictDecoderEncoderTests.java
@@ -646,7 +646,7 @@
         }
     }
 
-    public void testDeleteWord() {
+    private void runTestDeleteWord(final FormatOptions formatOptions) {
         final String dictName = "testDeleteWord";
         final String dictVersion = Long.toString(System.currentTimeMillis());
         final File file = setUpDictionaryFile(dictName, dictVersion);
@@ -655,10 +655,17 @@
                 new FusionDictionary.DictionaryOptions(
                         new HashMap<String, String>(), false, false));
         addUnigrams(sWords.size(), dict, sWords, null /* shortcutMap */);
-        timeWritingDictToFile(file, dict, VERSION3_WITH_DYNAMIC_UPDATE);
+        timeWritingDictToFile(file, dict, formatOptions);
 
-        final Ver3DictUpdater dictUpdater = new Ver3DictUpdater(file,
-                DictDecoder.USE_WRITABLE_BYTEBUFFER);
+        final DictUpdater dictUpdater;
+        if (formatOptions.mVersion == 3) {
+            dictUpdater = new Ver3DictUpdater(file, DictDecoder.USE_WRITABLE_BYTEBUFFER);
+        } else if (formatOptions.mVersion == 4) {
+            dictUpdater = new Ver4DictUpdater(file, DictDecoder.USE_WRITABLE_BYTEBUFFER);
+        } else {
+            throw new RuntimeException("DictUpdater for version " + formatOptions.mVersion
+                    + " doesn't exist.");
+        }
 
         try {
             MoreAsserts.assertNotEqual(FormatSpec.NOT_VALID_WORD,
@@ -676,4 +683,9 @@
         } catch (UnsupportedFormatException e) {
         }
     }
+
+    public void testDeleteWord() {
+        runTestDeleteWord(VERSION3_WITH_DYNAMIC_UPDATE);
+        runTestDeleteWord(VERSION4_WITH_DYNAMIC_UPDATE);
+    }
 }
diff --git a/tests/src/com/android/inputmethod/latin/makedict/BinaryDictIOUtilsTests.java b/tests/src/com/android/inputmethod/latin/makedict/BinaryDictIOUtilsTests.java
index acd6585..afe5adb 100644
--- a/tests/src/com/android/inputmethod/latin/makedict/BinaryDictIOUtilsTests.java
+++ b/tests/src/com/android/inputmethod/latin/makedict/BinaryDictIOUtilsTests.java
@@ -45,6 +45,9 @@
 
     private static final String TEST_DICT_FILE_EXTENSION = ".testDict";
 
+    private static final int VERSION3 = 3;
+    private static final int VERSION4 = 4;
+
     private static final String[] CHARACTERS = {
         "a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k", "l", "m",
         "n", "o", "p", "q", "r", "s", "t", "u", "v", "w", "x", "y", "z",
@@ -183,11 +186,16 @@
     // return amount of time to insert a word
     private long insertAndCheckWord(final File file, final String word, final int frequency,
             final boolean exist, final ArrayList<WeightedString> bigrams,
-            final ArrayList<WeightedString> shortcuts) {
+            final ArrayList<WeightedString> shortcuts, final int formatVersion) {
         long amountOfTime = -1;
         try {
-            final Ver3DictUpdater dictUpdater = new Ver3DictUpdater(file,
-                    DictDecoder.USE_WRITABLE_BYTEBUFFER);
+            final DictUpdater dictUpdater;
+            if (formatVersion == VERSION3) {
+                dictUpdater = new Ver3DictUpdater(file, DictDecoder.USE_WRITABLE_BYTEBUFFER);
+            } else {
+                throw new RuntimeException("DictUpdater for version " + formatVersion + " doesn't"
+                        + " exist.");
+            }
 
             if (!exist) {
                 assertEquals(FormatSpec.NOT_VALID_WORD, getWordPosition(file, word));
@@ -204,10 +212,15 @@
         return amountOfTime;
     }
 
-    private void deleteWord(final File file, final String word) {
+    private void deleteWord(final File file, final String word, final int formatVersion) {
         try {
-            final Ver3DictUpdater dictUpdater = new Ver3DictUpdater(file,
-                    DictDecoder.USE_WRITABLE_BYTEBUFFER);
+            final DictUpdater dictUpdater;
+            if (formatVersion == VERSION3) {
+                dictUpdater = new Ver3DictUpdater(file, DictDecoder.USE_WRITABLE_BYTEBUFFER);
+            } else {
+                throw new RuntimeException("DictUpdater for version " + formatVersion + " doesn't"
+                        + " exist.");
+            }
             dictUpdater.deleteWord(word);
         } catch (IOException e) {
         } catch (UnsupportedFormatException e) {
@@ -229,7 +242,7 @@
         }
     }
 
-    public void testInsertWord() {
+    private void runTestInsertWord(final int formatVersion) {
         File file = null;
         try {
             file = File.createTempFile("testInsertWord", TEST_DICT_FILE_EXTENSION,
@@ -253,33 +266,37 @@
         }
 
         MoreAsserts.assertNotEqual(FormatSpec.NOT_VALID_WORD, getWordPosition(file, "abcd"));
-        insertAndCheckWord(file, "abcde", 10, false, null, null);
+        insertAndCheckWord(file, "abcde", 10, false, null, null, formatVersion);
 
-        insertAndCheckWord(file, "abcdefghijklmn", 10, false, null, null);
+        insertAndCheckWord(file, "abcdefghijklmn", 10, false, null, null, formatVersion);
         checkReverseLookup(file, "abcdefghijklmn", getWordPosition(file, "abcdefghijklmn"));
 
-        insertAndCheckWord(file, "abcdabcd", 10, false, null, null);
+        insertAndCheckWord(file, "abcdabcd", 10, false, null, null, formatVersion);
         checkReverseLookup(file, "abcdabcd", getWordPosition(file, "abcdabcd"));
 
         // update the existing word.
-        insertAndCheckWord(file, "abcdabcd", 15, true, null, null);
+        insertAndCheckWord(file, "abcdabcd", 15, true, null, null, formatVersion);
 
         // split 1
-        insertAndCheckWord(file, "ab", 20, false, null, null);
+        insertAndCheckWord(file, "ab", 20, false, null, null, formatVersion);
 
         // split 2
-        insertAndCheckWord(file, "ami", 30, false, null, null);
+        insertAndCheckWord(file, "ami", 30, false, null, null, formatVersion);
 
-        deleteWord(file, "ami");
+        deleteWord(file, "ami", formatVersion);
         assertEquals(FormatSpec.NOT_VALID_WORD, getWordPosition(file, "ami"));
 
-        insertAndCheckWord(file, "abcdabfg", 30, false, null, null);
+        insertAndCheckWord(file, "abcdabfg", 30, false, null, null, formatVersion);
 
-        deleteWord(file, "abcd");
+        deleteWord(file, "abcd", formatVersion);
         assertEquals(FormatSpec.NOT_VALID_WORD, getWordPosition(file, "abcd"));
     }
 
-    public void testInsertWordWithBigrams() {
+    public void testInsertWord() {
+        runTestInsertWord(VERSION3);
+    }
+
+    private void runTestInsertWordWithBigrams(final int formatVersion) {
         File file = null;
         try {
             file = File.createTempFile("testInsertWordWithBigrams", TEST_DICT_FILE_EXTENSION,
@@ -306,8 +323,8 @@
         final ArrayList<WeightedString> banana = new ArrayList<WeightedString>();
         banana.add(new WeightedString("banana", 10));
 
-        insertAndCheckWord(file, "banana", 0, false, null, null);
-        insertAndCheckWord(file, "recursive", 60, true, banana, null);
+        insertAndCheckWord(file, "banana", 0, false, null, null, formatVersion);
+        insertAndCheckWord(file, "recursive", 60, true, banana, null, formatVersion);
 
         final PtNodeInfo info = findWordFromFile(file, "recursive");
         int bananaPos = getWordPosition(file, "banana");
@@ -316,7 +333,11 @@
         assertEquals(info.mBigrams.get(0).mAddress, bananaPos);
     }
 
-    public void testRandomWords() {
+    public void testInsertWordWithBigrams() {
+        runTestInsertWordWithBigrams(VERSION3);
+    }
+
+    private void runTestRandomWords(final int formatVersion) {
         File file = null;
         try {
             file = File.createTempFile("testRandomWord", TEST_DICT_FILE_EXTENSION,
@@ -345,7 +366,7 @@
         int cnt = 0;
         for (final String word : sWords) {
             final long diff = insertAndCheckWord(file, word,
-                    cnt % FormatSpec.MAX_TERMINAL_FREQUENCY, false, null, null);
+                    cnt % FormatSpec.MAX_TERMINAL_FREQUENCY, false, null, null, formatVersion);
             maxTimeToInsert = Math.max(maxTimeToInsert, diff);
             minTimeToInsert = Math.min(minTimeToInsert, diff);
             sum += diff;
@@ -356,8 +377,13 @@
             MoreAsserts.assertNotEqual(FormatSpec.NOT_VALID_WORD, getWordPosition(file, word));
         }
 
+        Log.d(TAG, "Test version " + formatVersion);
         Log.d(TAG, "max = " + ((double)maxTimeToInsert/1000000) + " ms.");
         Log.d(TAG, "min = " + ((double)minTimeToInsert/1000000) + " ms.");
         Log.d(TAG, "avg = " + ((double)sum/mMaxUnigrams/1000000) + " ms.");
     }
+
+    public void testRandomWords() {
+        runTestRandomWords(VERSION3);
+    }
 }