diff --git a/lib/CodeGen/PBQP.cpp b/lib/CodeGen/PBQP.cpp
index ade9e7ce532..00ca2a82f4b 100644
--- a/lib/CodeGen/PBQP.cpp
+++ b/lib/CodeGen/PBQP.cpp
@@ -15,6 +15,7 @@
 
 #include <limits>
 #include <cassert>
+#include <cstring>
 
 #include "PBQP.h"