diff --git a/clang/lib/Frontend/InitPreprocessor.cpp b/clang/lib/Frontend/InitPreprocessor.cpp
index 01a74d1..3a488bb 100644
--- a/clang/lib/Frontend/InitPreprocessor.cpp
+++ b/clang/lib/Frontend/InitPreprocessor.cpp
@@ -1128,6 +1128,7 @@
   if (AuxTriple.getOS() == llvm::Triple::Linux) {
     Builder.defineMacro("__ELF__");
     Builder.defineMacro("__linux__");
+    Builder.defineMacro("__gnu_linux__");
     // Used in features.h. If this is omitted, math.h doesn't declare float
     // versions of the functions in bits/mathcalls.h.
     if (LangOpts.CPlusPlus)