diff --git a/clang/include/clang/ASTMatchers/ASTMatchers.h b/clang/include/clang/ASTMatchers/ASTMatchers.h
--- a/clang/include/clang/ASTMatchers/ASTMatchers.h
+++ b/clang/include/clang/ASTMatchers/ASTMatchers.h
@@ -4872,7 +4872,7 @@
     }
   }
 
-  int ParamIndex = 0;
+  unsigned ParamIndex = 0;
   bool Matched = false;
   unsigned NumArgs = Node.getNumArgs();
   if (FProto && FProto->isVariadic())