1 files changed, 5 insertions, 0 deletions
diff --git a/re_comp.h b/re_comp.h
index 9539cac..39df590 100644
--- a/re_comp.h
+++ b/re_comp.h
@@ -27,6 +27,11 @@ OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 SOFTWARE.
 */
 
+#if defined _XOPEN_SOURCE && _XOPEN_SOURCE - 1 < 0
+#undef _XOPEN_SOURCE
+#define _XOPEN_SOURCE 400
+#endif
+
 #if	(defined _XOPEN_SOURCE && ((defined _XOPEN_SOURCE_EXTENDED && _XOPEN_SOURCE_EXTENDED == 1) || 500 <= _XOPEN_SOURCE) && _XOPEN_SOURCE < 600)
 /* ./src/re_comp/re_comp.c */
 char *re_comp(const char *__string);