diff --git a/clang/lib/Sema/SemaDeclAttr.cpp b/clang/lib/Sema/SemaDeclAttr.cpp
--- a/clang/lib/Sema/SemaDeclAttr.cpp
+++ b/clang/lib/Sema/SemaDeclAttr.cpp
@@ -3763,7 +3763,8 @@
   ParamIdx Idx;
   if (!checkFunctionOrMethodParameterIndex(S, D, AL, 1, IdxExpr, Idx))
     return;
-
+  if (Idx.getASTIndex() >= getFunctionOrMethodNumParams(D))
+    return;
   // Make sure the format string is really a string.
   QualType Ty = getFunctionOrMethodParamType(D, Idx.getASTIndex());