Index: include/bits/regex_constants.h
===================================================================
--- include/bits/regex_constants.h	(revision 201603)
+++ include/bits/regex_constants.h	(working copy)
@@ -77,7 +77,7 @@
    * elements @c ECMAScript, @c basic, @c extended, @c awk, @c grep, @c egrep
    * %set.
    */
-  typedef unsigned int syntax_option_type;
+  typedef unsigned short syntax_option_type;
 
   /**
    * Specifies that the matching of regular expressions against a character