diff --git a/libstdc++-v3/include/bits/regex_constants.h b/libstdc++-v3/include/bits/regex_constants.h
index 6ac65d7..03e25e2 100644
--- a/libstdc++-v3/include/bits/regex_constants.h
+++ b/libstdc++-v3/include/bits/regex_constants.h
@@ -77,7 +77,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
    * elements @c ECMAScript, @c basic, @c extended, @c awk, @c grep, @c egrep
    * %set.
    */
-  enum syntax_option_type
+  enum syntax_option_type : unsigned int
     {
       /**
        * Specifies that the matching of regular expressions against a character