diff --git a/src/gbm/main/gbm.c b/src/gbm/main/gbm.c
index c39cbfa7403..c046b1ad7c8 100644
--- a/src/gbm/main/gbm.c
+++ b/src/gbm/main/gbm.c
@@ -26,6 +26,7 @@
  */
 
 #define _BSD_SOURCE
+#define _DEFAULT_SOURCE
 
 #include <stddef.h>
 #include <stdio.h>