diff --git a/include/llvm/Option/OptSpecifier.h b/include/llvm/Option/OptSpecifier.h
index 02bc6b175ed..b7caa6e85a7 100644
--- a/include/llvm/Option/OptSpecifier.h
+++ b/include/llvm/Option/OptSpecifier.h
@@ -10,6 +10,8 @@
 #ifndef LLVM_OPTION_OPTSPECIFIER_H
 #define LLVM_OPTION_OPTSPECIFIER_H
 
+#include "llvm/Support/Compiler.h"
+
 namespace llvm {
 namespace opt {
   class Option;