diff --git a/native/jni/src/suggest/policyimpl/dictionary/structure/backward/v402/ver4_patricia_trie_policy.cpp b/native/jni/src/suggest/policyimpl/dictionary/structure/backward/v402/ver4_patricia_trie_policy.cpp
index 11f7b305f..cb07cbdad 100644
--- a/native/jni/src/suggest/policyimpl/dictionary/structure/backward/v402/ver4_patricia_trie_policy.cpp
+++ b/native/jni/src/suggest/policyimpl/dictionary/structure/backward/v402/ver4_patricia_trie_policy.cpp
@@ -428,7 +428,10 @@ 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);
     if (!addNgramEntry(prevWordsInfo, &ngramProperty)) {
         AKLOGE("Cannot update unigarm entry in updateCounter().");
         return false;
diff --git a/tests/src/com/android/inputmethod/latin/BinaryDictionaryDecayingTests.java b/tests/src/com/android/inputmethod/latin/BinaryDictionaryDecayingTests.java
index c3c2bb2fd..cbfbab926 100644
--- a/tests/src/com/android/inputmethod/latin/BinaryDictionaryDecayingTests.java
+++ b/tests/src/com/android/inputmethod/latin/BinaryDictionaryDecayingTests.java
@@ -611,6 +611,7 @@ public class BinaryDictionaryDecayingTests extends AndroidTestCase {
                 mCurrentTime);
         final NgramContext beginningOfSentenceContext = NgramContext.BEGINNING_OF_SENTENCE;
         onInputWordWithBeginningOfSentenceContext(binaryDictionary, "aaa", true /* isValidWord */);
+        onInputWordWithBeginningOfSentenceContext(binaryDictionary, "aaa", true /* isValidWord */);
         assertTrue(binaryDictionary.isValidNgram(beginningOfSentenceContext, "aaa"));
         onInputWordWithBeginningOfSentenceContext(binaryDictionary, "aaa", true /* isValidWord */);
         onInputWordWithBeginningOfSentenceContext(binaryDictionary, "bbb", true /* isValidWord */);
@@ -622,6 +623,8 @@ public class BinaryDictionaryDecayingTests extends AndroidTestCase {
         assertFalse(binaryDictionary.isValidNgram(beginningOfSentenceContext, "bbb"));
 
         onInputWordWithBeginningOfSentenceContext(binaryDictionary, "aaa", true /* isValidWord */);
+        onInputWordWithBeginningOfSentenceContext(binaryDictionary, "aaa", true /* isValidWord */);
+        onInputWordWithBeginningOfSentenceContext(binaryDictionary, "bbb", true /* isValidWord */);
         onInputWordWithBeginningOfSentenceContext(binaryDictionary, "bbb", true /* isValidWord */);
         assertTrue(binaryDictionary.isValidNgram(beginningOfSentenceContext, "aaa"));
         assertTrue(binaryDictionary.isValidNgram(beginningOfSentenceContext, "bbb"));