diff --git a/clang/include/clang/AST/ASTContext.h b/clang/include/clang/AST/ASTContext.h
index 324185f0900cacf2b413dd1378b31963af314926..9361ebea1b21391a0b3fa24f834454fb643f2490 100644
--- a/clang/include/clang/AST/ASTContext.h
+++ b/clang/include/clang/AST/ASTContext.h
@@ -457,7 +457,7 @@ public:
     return BumpAlloc;
   }
 
-  void *Allocate(unsigned Size, unsigned Align = 8) const {
+  void *Allocate(size_t Size, unsigned Align = 8) const {
     return BumpAlloc.Allocate(Size, Align);
   }
   void Deallocate(void *Ptr) const { }