diff --git a/native/jni/src/defines.h b/native/jni/src/defines.h
index 0e67b4d..10b930e 100644
--- a/native/jni/src/defines.h
+++ b/native/jni/src/defines.h
@@ -275,7 +275,7 @@
 #define MAX_POINTER_COUNT_G 2
 
 // (MAX_PREV_WORD_COUNT_FOR_N_GRAM + 1)-gram is supported.
-#define MAX_PREV_WORD_COUNT_FOR_N_GRAM 2
+#define MAX_PREV_WORD_COUNT_FOR_N_GRAM 3
 
 #define DISALLOW_DEFAULT_CONSTRUCTOR(TypeName) \
   TypeName() = delete
diff --git a/native/jni/src/suggest/policyimpl/dictionary/header/header_policy.cpp b/native/jni/src/suggest/policyimpl/dictionary/header/header_policy.cpp
index a2a0f11..c93f310 100644
--- a/native/jni/src/suggest/policyimpl/dictionary/header/header_policy.cpp
+++ b/native/jni/src/suggest/policyimpl/dictionary/header/header_policy.cpp
@@ -31,10 +31,11 @@
 const char *const HeaderPolicy::DATE_KEY = "date";
 const char *const HeaderPolicy::LAST_DECAYED_TIME_KEY = "LAST_DECAYED_TIME";
 const char *const HeaderPolicy::NGRAM_COUNT_KEYS[] =
-        {"UNIGRAM_COUNT", "BIGRAM_COUNT", "TRIGRAM_COUNT"};
+        {"UNIGRAM_COUNT", "BIGRAM_COUNT", "TRIGRAM_COUNT", "QUADGRAM_COUNT"};
 const char *const HeaderPolicy::MAX_NGRAM_COUNT_KEYS[] =
-        {"MAX_UNIGRAM_ENTRY_COUNT", "MAX_BIGRAM_ENTRY_COUNT", "MAX_TRIGRAM_ENTRY_COUNT"};
-const int HeaderPolicy::DEFAULT_MAX_NGRAM_COUNTS[] = {10000, 30000, 30000};
+        {"MAX_UNIGRAM_ENTRY_COUNT", "MAX_BIGRAM_ENTRY_COUNT", "MAX_TRIGRAM_ENTRY_COUNT",
+                "MAX_QUADGRAM_ENTRY_COUNT"};
+const int HeaderPolicy::DEFAULT_MAX_NGRAM_COUNTS[] = {10000, 30000, 30000, 30000};
 const char *const HeaderPolicy::EXTENDED_REGION_SIZE_KEY = "EXTENDED_REGION_SIZE";
 // Historical info is information that is needed to support decaying such as timestamp, level and
 // count.
diff --git a/native/jni/src/suggest/policyimpl/dictionary/structure/v4/content/dynamic_language_model_probability_utils.cpp b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/content/dynamic_language_model_probability_utils.cpp
index 29bc7f7..025ee99 100644
--- a/native/jni/src/suggest/policyimpl/dictionary/structure/v4/content/dynamic_language_model_probability_utils.cpp
+++ b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/content/dynamic_language_model_probability_utils.cpp
@@ -19,12 +19,13 @@
 namespace latinime {
 
 // Used to provide stable probabilities even if the user's input count is small.
-const int DynamicLanguageModelProbabilityUtils::ASSUMED_MIN_COUNTS[] = {8192, 2, 2};
+const int DynamicLanguageModelProbabilityUtils::ASSUMED_MIN_COUNTS[] = {8192, 2, 2, 1};
 
 // Encoded backoff weights.
-// Note that we give positive value for trigrams that means the weight is more than 1.
+// Note that we give positive values for trigrams and quadgrams that means the weight is more than
+// 1.
 // TODO: Apply backoff for main dictionaries and quit giving a positive backoff weight.
-const int DynamicLanguageModelProbabilityUtils::ENCODED_BACKOFF_WEIGHTS[] = {-32, 0, 8};
+const int DynamicLanguageModelProbabilityUtils::ENCODED_BACKOFF_WEIGHTS[] = {-32, -4, 2, 8};
 
 // This value is used to remove too old entries from the dictionary.
 const int DynamicLanguageModelProbabilityUtils::DURATION_TO_DISCARD_ENTRY_IN_SECONDS =
diff --git a/native/jni/src/suggest/policyimpl/dictionary/structure/v4/content/dynamic_language_model_probability_utils.h b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/content/dynamic_language_model_probability_utils.h
index b38047f..644ae2c 100644
--- a/native/jni/src/suggest/policyimpl/dictionary/structure/v4/content/dynamic_language_model_probability_utils.h
+++ b/native/jni/src/suggest/policyimpl/dictionary/structure/v4/content/dynamic_language_model_probability_utils.h
@@ -66,7 +66,7 @@
 private:
     DISALLOW_IMPLICIT_CONSTRUCTORS(DynamicLanguageModelProbabilityUtils);
 
-    static_assert(MAX_PREV_WORD_COUNT_FOR_N_GRAM <= 2, "Max supported Ngram is Trigram.");
+    static_assert(MAX_PREV_WORD_COUNT_FOR_N_GRAM <= 3, "Max supported Ngram is Quadgram.");
 
     static const int ASSUMED_MIN_COUNTS[];
     static const int ENCODED_BACKOFF_WEIGHTS[];
diff --git a/native/jni/src/suggest/policyimpl/dictionary/utils/entry_counters.h b/native/jni/src/suggest/policyimpl/dictionary/utils/entry_counters.h
index 7269913..5e44302 100644
--- a/native/jni/src/suggest/policyimpl/dictionary/utils/entry_counters.h
+++ b/native/jni/src/suggest/policyimpl/dictionary/utils/entry_counters.h
@@ -27,7 +27,7 @@
 // Copyable but immutable
 class EntryCounts final {
  public:
-    EntryCounts() : mEntryCounts({{0, 0, 0}}) {}
+    EntryCounts() : mEntryCounts({{0, 0, 0, 0}}) {}
 
     explicit EntryCounts(const std::array<int, MAX_PREV_WORD_COUNT_FOR_N_GRAM + 1> &counters)
             : mEntryCounts(counters) {}
diff --git a/native/jni/src/utils/ngram_utils.h b/native/jni/src/utils/ngram_utils.h
index 6227812..fa85ba3 100644
--- a/native/jni/src/utils/ngram_utils.h
+++ b/native/jni/src/utils/ngram_utils.h
@@ -25,6 +25,7 @@
     Unigram = 0,
     Bigram = 1,
     Trigram = 2,
+    Quadgram = 3,
     NotANgramType = -1,
 };