--- a/src/dir.c	2018-12-18 12:11:40.000000000 +0100
+++ b/src/dir.c	2020-02-27 19:32:00.653813072 +0100
@@ -31,7 +31,7 @@
   IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
 
-
+#define _GNU_SOURCE /* for asprintf(3) */
 #include <errno.h>
 #include <limits.h>
 #include <stdio.h>
--- a/src/ckmame.c	2018-12-18 12:11:40.000000000 +0100
+++ b/src/ckmame.c	2020-02-27 19:39:05.451796134 +0100
@@ -33,6 +33,7 @@
 
 #include "config.h"
 
+#define _GNU_SOURCE /* for asprintf(3) */
 #include <signal.h>
 #include <stdio.h>
 #include <stdlib.h>
--- a/src/xmalloc.c	2018-12-18 12:11:40.000000000 +0100
+++ b/src/xmalloc.c	2020-02-27 19:40:48.957792007 +0100
@@ -33,6 +33,7 @@
 
 #include "config.h"
 
+#define _GNU_SOURCE /* for vasprintf(3) */
 #include <errno.h>
 #include <stdio.h>
 #include <stdlib.h>