diff --git a/include/llvm/ADT/BitVector.h b/include/llvm/ADT/BitVector.h
index 79c3f585677..269621313fa 100644
--- a/include/llvm/ADT/BitVector.h
+++ b/include/llvm/ADT/BitVector.h
@@ -290,12 +290,10 @@ private:
 
   // Clear the unused top bits in the high word.
   void clear_unused_bits() {
-    if (Size) {
-      unsigned ExtraBits = Size % BITS_PER_WORD;
+    unsigned ExtraBits = Size % BITS_PER_WORD;
+    if (ExtraBits) {
       unsigned index = Size / BITS_PER_WORD;
-      if (Size % BITS_PER_WORD == 0)
-        index--;
-      Bits[index] &= ~(~0 << ExtraBits);
+      Bits[index] &= ~(~0L << ExtraBits);
     }
   }