diff --git a/include/llvm/Support/Mangler.h b/include/llvm/Support/Mangler.h
index 502b7973439..533b44f5256 100644
--- a/include/llvm/Support/Mangler.h
+++ b/include/llvm/Support/Mangler.h
@@ -11,6 +11,7 @@ class Value;
 class Module;
 #include <map>
 #include <set>
+#include <string>
 
 class Mangler {
 public: