diff --git a/lib/TableGen/TGLexer.cpp b/lib/TableGen/TGLexer.cpp
index c9c674c8898..79d9ed29f90 100644
--- a/lib/TableGen/TGLexer.cpp
+++ b/lib/TableGen/TGLexer.cpp
@@ -23,7 +23,7 @@
 #include <cstring>
 #include <cerrno>
 
-#include "llvm/Config/config.h"
+#include "llvm/Config/config.h" // for strtoull()/strtoll() define
 
 using namespace llvm;