===================================================================
RCS file: /cvsrepo/anoncvs/cvs/src/usr.bin/tmux/format.c,v
retrieving revision 1.66
retrieving revision 1.67
diff -u -r1.66 -r1.67
--- src/usr.bin/tmux/format.c	2015/05/12 15:29:29	1.66
+++ src/usr.bin/tmux/format.c	2015/05/20 06:39:02	1.67
@@ -1,4 +1,4 @@
-/* $OpenBSD: format.c,v 1.66 2015/05/12 15:29:29 nicm Exp $ */
+/* $OpenBSD: format.c,v 1.67 2015/05/20 06:39:02 nicm Exp $ */
 
 /*
  * Copyright (c) 2011 Nicholas Marriott <nicm@users.sourceforge.net>
@@ -335,7 +335,7 @@
 	size_t		 tmplen;
 	struct tm	*tm;
 
-	if (fmt == NULL)
+	if (fmt == NULL || *fmt == '\0')
 		return (xstrdup(""));
 
 	tm = localtime(&t);