diff --git a/src/core/display.c b/src/core/display.c
index d5024e5cb..8e3f93a42 100644
--- a/src/core/display.c
+++ b/src/core/display.c
@@ -28,8 +28,6 @@
  * The display is represented as a #MetaDisplay struct.
  */
 
-#define _XOPEN_SOURCE 600 /* for gethostname() */
-
 #include "config.h"
 
 #include <stdlib.h>