diff --git a/clang/lib/Frontend/InitPreprocessor.cpp b/clang/lib/Frontend/InitPreprocessor.cpp
index 30bf118..15aa546 100644
--- a/clang/lib/Frontend/InitPreprocessor.cpp
+++ b/clang/lib/Frontend/InitPreprocessor.cpp
@@ -411,6 +411,8 @@
   // Not "standard" per se, but available even with the -undef flag.
   if (LangOpts.AsmPreprocessor)
     Builder.defineMacro("__ASSEMBLER__");
+  if (LangOpts.CUDA)
+    Builder.defineMacro("__CUDA__");
 }
 
 /// Initialize the predefined C++ language feature test macros defined in