diff --git a/clang/test/Sema/constant-builtins-fmax.cpp b/clang/test/Sema/constant-builtins-fmax.cpp
--- a/clang/test/Sema/constant-builtins-fmax.cpp
+++ b/clang/test/Sema/constant-builtins-fmax.cpp
@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -fsyntax-only -verify %s
+// RUN: %clang_cc1 -std=c++17 -fsyntax-only -verify %s
 // expected-no-diagnostics
 
 constexpr double NaN = __builtin_nan("");