diff --git a/lib/Transforms/IPO/SimplifyLibCalls.cpp b/lib/Transforms/IPO/SimplifyLibCalls.cpp
index 951516a1842..c7734a814f8 100644
--- a/lib/Transforms/IPO/SimplifyLibCalls.cpp
+++ b/lib/Transforms/IPO/SimplifyLibCalls.cpp
@@ -27,6 +27,7 @@
 #include "llvm/Support/Debug.h"
 #include "llvm/Target/TargetData.h"
 #include "llvm/Transforms/IPO.h"
+#include "llvm/Config/config.h"
 #include <iostream>
 using namespace llvm;