diff --git a/include/llvm/User.h b/include/llvm/User.h
index 42f9c861016..eab7a96e46b 100644
--- a/include/llvm/User.h
+++ b/include/llvm/User.h
@@ -13,6 +13,7 @@
 #define LLVM_USER_H
 
 #include "llvm/Value.h"
+#include <vector>
 
 class User : public Value {
   User(const User &);             // Do not implement