diff --git a/include/llvm/ADT/DenseMap.h b/include/llvm/ADT/DenseMap.h
index 9d2b11d6b2b..36e96b8c3d0 100644
--- a/include/llvm/ADT/DenseMap.h
+++ b/include/llvm/ADT/DenseMap.h
@@ -422,7 +422,8 @@ private:
     }
 
 #ifndef NDEBUG
-    memset(OldBuckets, 0x5a, sizeof(BucketT)*OldNumBuckets);
+    if (OldNumBuckets)
+      memset(OldBuckets, 0x5a, sizeof(BucketT)*OldNumBuckets);
 #endif
     // Free the old table.
     operator delete(OldBuckets);