diff --git a/include/boost/regex/v4/match_flags.hpp b/include/boost/regex/v4/match_flags.hpp
index 5fa0b075..1c0046b7 100644
--- a/include/boost/regex/v4/match_flags.hpp
+++ b/include/boost/regex/v4/match_flags.hpp
@@ -22,6 +22,7 @@
 #ifdef __cplusplus
 #  include <boost/cstdint.hpp>
 #endif
+#include <boost/detail/workaround.hpp>
 
 #ifdef __cplusplus
 namespace boost{