===================================================================
RCS file: /cvsrepo/anoncvs/cvs/src/usr.bin/tmux/cmd-set-environment.c,v
retrieving revision 1.17
retrieving revision 1.18
diff -u -r1.17 -r1.18
--- src/usr.bin/tmux/cmd-set-environment.c	2016/01/19 15:59:12	1.17
+++ src/usr.bin/tmux/cmd-set-environment.c	2016/03/03 14:15:22	1.18
@@ -1,4 +1,4 @@
-/* $OpenBSD: cmd-set-environment.c,v 1.17 2016/01/19 15:59:12 nicm Exp $ */
+/* $OpenBSD: cmd-set-environment.c,v 1.18 2016/03/03 14:15:22 nicm Exp $ */
 
 /*
  * Copyright (c) 2009 Nicholas Marriott <nicholas.marriott@gmail.com>
@@ -47,7 +47,7 @@
 {
 	struct args	*args = self->args;
 	struct environ	*env;
-	const char	*name, *value;
+	const char	*name, *value, *target;
 
 	name = args->argv[0];
 	if (*name == '\0') {
@@ -64,10 +64,19 @@
 	else
 		value = args->argv[1];
 
-	if (args_has(self->args, 'g') || cmdq->state.tflag.s == NULL)
+	if (args_has(self->args, 'g'))
 		env = global_environ;
-	else
+	else {
+		if (cmdq->state.tflag.s == NULL) {
+			target = args_get(args, 't');
+			if (target != NULL)
+				cmdq_error(cmdq, "no such session: %s", target);
+			else
+				cmdq_error(cmdq, "no current session");
+			return (CMD_RETURN_ERROR);
+		}
 		env = cmdq->state.tflag.s->environ;
+	}
 
 	if (args_has(self->args, 'u')) {
 		if (value != NULL) {