diff --git a/Lex/Preprocessor.cpp b/Lex/Preprocessor.cpp
index 104fb65152..9c2683315f 100644
--- a/Lex/Preprocessor.cpp
+++ b/Lex/Preprocessor.cpp
@@ -37,6 +37,7 @@
 #include "clang/Basic/TargetInfo.h"
 #include "llvm/ADT/SmallVector.h"
 #include <iostream>
+#include <alloca.h>
 using namespace clang;
 
 //===----------------------------------------------------------------------===//