diff --git a/include/llvm/ADT/SmallVector.h b/include/llvm/ADT/SmallVector.h
index bb8cef4ce8a..876ca27fec7 100644
--- a/include/llvm/ADT/SmallVector.h
+++ b/include/llvm/ADT/SmallVector.h
@@ -442,7 +442,7 @@ public:
   SmallVector() : SmallVectorImpl<T>(NumTsAvailable) {
   }
   
-  SmallVector(unsigned Size, const T &Value = T())
+  explicit SmallVector(unsigned Size, const T &Value = T())
     : SmallVectorImpl<T>(NumTsAvailable) {
     this->reserve(Size);
     while (Size--)