diff --git a/lib/Fuzzer/FuzzerValueBitMap.h b/lib/Fuzzer/FuzzerValueBitMap.h
index 493afc574cc..65659f21349 100644
--- a/lib/Fuzzer/FuzzerValueBitMap.h
+++ b/lib/Fuzzer/FuzzerValueBitMap.h
@@ -26,7 +26,7 @@ struct ValueBitMap {
 
   // Computed a hash function of Value and sets the corresponding bit.
   void AddValue(uintptr_t Value) {
-    uintptr_t Idx = Value % kMapSizeInBits;
+    uintptr_t Idx = Value < kMapSizeInBits ? Value : Value % kMapSizeInBits;
     uintptr_t WordIdx = Idx / kBitsInWord;
     uintptr_t BitIdx = Idx % kBitsInWord;
     Map[WordIdx] |= 1UL << BitIdx;