diff --git a/clang/lib/Sema/SemaChecking.cpp b/clang/lib/Sema/SemaChecking.cpp
index cd069d566457..f575c0775e7f 100644
--- a/clang/lib/Sema/SemaChecking.cpp
+++ b/clang/lib/Sema/SemaChecking.cpp
@@ -6222,7 +6222,7 @@ static bool checkBuiltinArgument(Sema &S, CallExpr *E, unsigned ArgIndex) {
   InitializedEntity Entity =
     InitializedEntity::InitializeParameter(S.Context, Param);
 
-  ExprResult Arg = E->getArg(0);
+  ExprResult Arg = E->getArg(ArgIndex);
   Arg = S.PerformCopyInitialization(Entity, SourceLocation(), Arg);
   if (Arg.isInvalid())
     return true;