diff --git a/clang/lib/Sema/ParsedAttr.cpp b/clang/lib/Sema/ParsedAttr.cpp
--- a/clang/lib/Sema/ParsedAttr.cpp
+++ b/clang/lib/Sema/ParsedAttr.cpp
@@ -111,7 +111,7 @@
 
 const ParsedAttrInfo &ParsedAttrInfo::get(const AttributeCommonInfo &A) {
   // If we have a ParsedAttrInfo for this ParsedAttr then return that.
-  if (A.getParsedKind() < llvm::array_lengthof(AttrInfoMap))
+  if ((size_t)A.getParsedKind() < llvm::array_lengthof(AttrInfoMap))
     return *AttrInfoMap[A.getParsedKind()];
 
   // If this is an ignored attribute then return an appropriate ParsedAttrInfo.