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 0675de6..85d6d43 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
@@ -167,6 +167,14 @@
     if (lastBitmapEntryIndex == TrieMap::INVALID_INDEX) {
         return TrieMap::INVALID_INDEX;
     }
+    const int oldestPrevWordId = prevWordIds[prevWordIds.size() - 1];
+    const TrieMap::Result result = mTrieMap.get(oldestPrevWordId, lastBitmapEntryIndex);
+    if (!result.mIsValid) {
+        if (!mTrieMap.put(oldestPrevWordId,
+                ProbabilityEntry().encode(mHasHistoricalInfo), lastBitmapEntryIndex)) {
+            return TrieMap::INVALID_INDEX;
+        }
+    }
     return mTrieMap.getNextLevelBitmapEntryIndex(prevWordIds[prevWordIds.size() - 1],
             lastBitmapEntryIndex);
 }
diff --git a/native/jni/src/suggest/policyimpl/dictionary/structure/v4/content/probability_entry.h b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/content/probability_entry.h
index 3dfaba7..f1bf12c 100644
--- a/native/jni/src/suggest/policyimpl/dictionary/structure/v4/content/probability_entry.h
+++ b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/content/probability_entry.h
@@ -36,7 +36,8 @@
 
     // Dummy entry
     ProbabilityEntry()
-            : mFlags(0), mProbability(NOT_A_PROBABILITY), mHistoricalInfo() {}
+            : mFlags(Ver4DictConstants::FLAG_NOT_A_VALID_ENTRY), mProbability(NOT_A_PROBABILITY),
+              mHistoricalInfo() {}
 
     // Entry without historical information
     ProbabilityEntry(const int flags, const int probability)
@@ -61,7 +62,7 @@
                       bigramProperty->getCount()) {}
 
     bool isValid() const {
-        return (mProbability != NOT_A_PROBABILITY) || hasHistoricalInfo();
+        return (mFlags & Ver4DictConstants::FLAG_NOT_A_VALID_ENTRY) == 0;
     }
 
     bool hasHistoricalInfo() const {
diff --git a/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_dict_constants.cpp b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_dict_constants.cpp
index 9acf2d4..39822b9 100644
--- a/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_dict_constants.cpp
+++ b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_dict_constants.cpp
@@ -53,6 +53,7 @@
 const int Ver4DictConstants::WORD_COUNT_FIELD_SIZE = 1;
 
 const uint8_t Ver4DictConstants::FLAG_REPRESENTS_BEGINNING_OF_SENTENCE = 0x1;
+const uint8_t Ver4DictConstants::FLAG_NOT_A_VALID_ENTRY = 0x2;
 
 const int Ver4DictConstants::SHORTCUT_ADDRESS_TABLE_BLOCK_SIZE = 64;
 const int Ver4DictConstants::SHORTCUT_ADDRESS_TABLE_DATA_SIZE = 4;
diff --git a/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_dict_constants.h b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_dict_constants.h
index 9703531..dfcdd4d 100644
--- a/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_dict_constants.h
+++ b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/ver4_dict_constants.h
@@ -51,6 +51,7 @@
     static const int WORD_COUNT_FIELD_SIZE;
     // Flags in probability entry.
     static const uint8_t FLAG_REPRESENTS_BEGINNING_OF_SENTENCE;
+    static const uint8_t FLAG_NOT_A_VALID_ENTRY;
 
     static const int SHORTCUT_ADDRESS_TABLE_BLOCK_SIZE;
     static const int SHORTCUT_ADDRESS_TABLE_DATA_SIZE;
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 b808c90..2af218a 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
@@ -120,16 +120,15 @@
     const int ptNodePos =
             mBuffers->getTerminalPositionLookupTable()->getTerminalPtNodePosition(wordId);
     const PtNodeParams ptNodeParams = mNodeReader.fetchPtNodeParamsInBufferFromPtNodePos(ptNodePos);
-    // TODO: Support n-gram.
     const int probability = mBuffers->getLanguageModelDictContent()->getWordProbability(
-            prevWordIds.limit(1 /* maxSize */), wordId, mHeaderPolicy);
+            prevWordIds, wordId, mHeaderPolicy);
     return WordAttributes(probability, ptNodeParams.isBlacklisted(), ptNodeParams.isNotAWord(),
             probability == 0);
 }
 
 int Ver4PatriciaTriePolicy::getProbabilityOfWord(const WordIdArrayView prevWordIds,
         const int wordId) const {
-    if (wordId == NOT_A_WORD_ID) {
+    if (wordId == NOT_A_WORD_ID || prevWordIds.contains(NOT_A_WORD_ID)) {
         return NOT_A_PROBABILITY;
     }
     const int ptNodePos =
@@ -138,10 +137,8 @@
     if (ptNodeParams.isDeleted() || ptNodeParams.isBlacklisted() || ptNodeParams.isNotAWord()) {
         return NOT_A_PROBABILITY;
     }
-    // TODO: Support n-gram.
     const ProbabilityEntry probabilityEntry =
-            mBuffers->getLanguageModelDictContent()->getNgramProbabilityEntry(
-                    prevWordIds.limit(1 /* maxSize */), wordId);
+            mBuffers->getLanguageModelDictContent()->getNgramProbabilityEntry(prevWordIds, wordId);
     if (!probabilityEntry.isValid()) {
         return NOT_A_PROBABILITY;
     }
@@ -164,16 +161,18 @@
     if (prevWordIds.empty()) {
         return;
     }
-    // TODO: Support n-gram.
     const auto languageModelDictContent = mBuffers->getLanguageModelDictContent();
-    for (const auto entry : languageModelDictContent->getProbabilityEntries(
-            prevWordIds.limit(1 /* maxSize */))) {
-        const ProbabilityEntry &probabilityEntry = entry.getProbabilityEntry();
-        const int probability = probabilityEntry.hasHistoricalInfo() ?
-                ForgettingCurveUtils::decodeProbability(
-                        probabilityEntry.getHistoricalInfo(), mHeaderPolicy) :
-                probabilityEntry.getProbability();
-        listener->onVisitEntry(probability, entry.getWordId());
+    for (size_t i = 1; i <= prevWordIds.size(); ++i) {
+        for (const auto entry : languageModelDictContent->getProbabilityEntries(
+                prevWordIds.limit(i))) {
+            const ProbabilityEntry &probabilityEntry = entry.getProbabilityEntry();
+            const int probability = probabilityEntry.hasHistoricalInfo() ?
+                    ForgettingCurveUtils::decodeProbability(
+                            probabilityEntry.getHistoricalInfo(), mHeaderPolicy)
+                            + ForgettingCurveUtils::getProbabilityBiasForNgram(i + 1 /* n */) :
+                    probabilityEntry.getProbability();
+            listener->onVisitEntry(probability, entry.getWordId());
+        }
     }
 }
 
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 c5849d0..06f82df 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
@@ -29,7 +29,7 @@
 TEST(LanguageModelDictContentTest, TestUnigramProbability) {
     LanguageModelDictContent languageModelDictContent(false /* useHistoricalInfo */);
 
-    const int flag = 0xFF;
+    const int flag = 0xF0;
     const int probability = 10;
     const int wordId = 100;
     const ProbabilityEntry probabilityEntry(flag, probability);