diff --git a/cmd-new-session.c b/cmd-new-session.c
index 6818ce9c..2fd13420 100644
--- a/cmd-new-session.c
+++ b/cmd-new-session.c
@@ -192,6 +192,8 @@ cmd_new_session_exec(struct cmd *self, struct cmdq_item *item)
 		if (strcmp(tmp, "-") == 0) {
 			if (c != NULL)
 				dsx = c->tty.sx;
+			else
+				dsx = 80;
 		} else {
 			dsx = strtonum(tmp, 1, USHRT_MAX, &errstr);
 			if (errstr != NULL) {
@@ -205,6 +207,8 @@ cmd_new_session_exec(struct cmd *self, struct cmdq_item *item)
 		if (strcmp(tmp, "-") == 0) {
 			if (c != NULL)
 				dsy = c->tty.sy;
+			else
+				dsy = 24;
 		} else {
 			dsy = strtonum(tmp, 1, USHRT_MAX, &errstr);
 			if (errstr != NULL) {