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 41b109f95..036197c41 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
@@ -378,7 +378,10 @@ bool Ver4PatriciaTriePolicy::updateCounter(const PrevWordsInfo *const prevWordsI
         AKLOGE("Cannot update unigarm entry in updateCounter().");
         return false;
     }
-    const NgramProperty ngramProperty(wordCodePoints.toVector(), probability, historicalInfo);
+    const int probabilityForNgram = prevWordsInfo->isNthPrevWordBeginningOfSentence(1 /* n */)
+            ? NOT_A_PROBABILITY : probability;
+    const NgramProperty ngramProperty(wordCodePoints.toVector(), probabilityForNgram,
+            historicalInfo);
     for (size_t i = 1; i <= prevWordsInfo->getPrevWordCount(); ++i) {
         const PrevWordsInfo trimmedPrevWordsInfo(prevWordsInfo->getTrimmedPrevWordsInfo(i));
         if (!addNgramEntry(&trimmedPrevWordsInfo, &ngramProperty)) {
diff --git a/tests/src/com/android/inputmethod/latin/BinaryDictionaryDecayingTests.java b/tests/src/com/android/inputmethod/latin/BinaryDictionaryDecayingTests.java
index cbfbab926..0e58b7211 100644
--- a/tests/src/com/android/inputmethod/latin/BinaryDictionaryDecayingTests.java
+++ b/tests/src/com/android/inputmethod/latin/BinaryDictionaryDecayingTests.java
@@ -611,20 +611,23 @@ public class BinaryDictionaryDecayingTests extends AndroidTestCase {
                 mCurrentTime);
         final NgramContext beginningOfSentenceContext = NgramContext.BEGINNING_OF_SENTENCE;
         onInputWordWithBeginningOfSentenceContext(binaryDictionary, "aaa", true /* isValidWord */);
+        assertFalse(binaryDictionary.isValidNgram(beginningOfSentenceContext, "aaa"));
         onInputWordWithBeginningOfSentenceContext(binaryDictionary, "aaa", true /* isValidWord */);
         assertTrue(binaryDictionary.isValidNgram(beginningOfSentenceContext, "aaa"));
         onInputWordWithBeginningOfSentenceContext(binaryDictionary, "aaa", true /* isValidWord */);
         onInputWordWithBeginningOfSentenceContext(binaryDictionary, "bbb", true /* isValidWord */);
+        assertFalse(binaryDictionary.isValidNgram(beginningOfSentenceContext, "bbb"));
         onInputWordWithBeginningOfSentenceContext(binaryDictionary, "bbb", true /* isValidWord */);
         assertTrue(binaryDictionary.isValidNgram(beginningOfSentenceContext, "aaa"));
         assertTrue(binaryDictionary.isValidNgram(beginningOfSentenceContext, "bbb"));
         forcePassingLongTime(binaryDictionary);
         assertFalse(binaryDictionary.isValidNgram(beginningOfSentenceContext, "aaa"));
         assertFalse(binaryDictionary.isValidNgram(beginningOfSentenceContext, "bbb"));
-
         onInputWordWithBeginningOfSentenceContext(binaryDictionary, "aaa", true /* isValidWord */);
+        assertFalse(binaryDictionary.isValidNgram(beginningOfSentenceContext, "aaa"));
         onInputWordWithBeginningOfSentenceContext(binaryDictionary, "aaa", true /* isValidWord */);
         onInputWordWithBeginningOfSentenceContext(binaryDictionary, "bbb", true /* isValidWord */);
+        assertFalse(binaryDictionary.isValidNgram(beginningOfSentenceContext, "bbb"));
         onInputWordWithBeginningOfSentenceContext(binaryDictionary, "bbb", true /* isValidWord */);
         assertTrue(binaryDictionary.isValidNgram(beginningOfSentenceContext, "aaa"));
         assertTrue(binaryDictionary.isValidNgram(beginningOfSentenceContext, "bbb"));