Index: clang/test/Preprocessor/lang-std.cpp
===================================================================
--- clang/test/Preprocessor/lang-std.cpp
+++ clang/test/Preprocessor/lang-std.cpp
@@ -1,7 +1,10 @@
 /// Test default standards.
-/// CUDA/HIP uses the same default standards as C++.
 
 // RUN: %clang_cc1 -dM -E %s | grep __cplusplus >%T-cpp-std.txt
+// RUN: cat %T-cpp-std.txt | FileCheck --check-prefix=CXX17 %s
+
+/// Check that CUDA/HIP uses the same default standards as C++.
+
 // RUN: %clang_cc1 -dM -E -x cuda %s | grep __cplusplus >%T-cuda-cuda.txt
 // RUN: %clang_cc1 -dM -E -x hip %s | grep __cplusplus >%T-hip-std.txt
 // RUN: diff %T-cpp-std.txt %T-cuda-cuda.txt