diff --git a/git-compat-util.h b/git-compat-util.h
index f587749b7c..fd165884f2 100644
--- a/git-compat-util.h
+++ b/git-compat-util.h
@@ -82,6 +82,7 @@
 #define _ALL_SOURCE 1
 #define _GNU_SOURCE 1
 #define _BSD_SOURCE 1
+#define _DEFAULT_SOURCE 1
 #define _NETBSD_SOURCE 1
 #define _SGI_SOURCE 1