diff --git a/src/service.c b/src/service.c
index 52068044..2ca0260f 100644
--- a/src/service.c
+++ b/src/service.c
@@ -1227,7 +1227,11 @@ int service_register(int type, char *cfg, struct rlimit rlimit[], char *file)
 		if (tty_parse_args(cmd, &tty))
 			return errno;
 
-		len += strlen(tty.cmd) + tty.num + 1;
+		if (tty.cmd)
+			len += strlen(tty.cmd);
+		else
+			len += 3;
+		len += tty.num + 1;
 		for (i = 0; i < tty.num; i++)
 			len += strlen(tty.args[i]) + 1;
 
@@ -1235,7 +1239,7 @@ int service_register(int type, char *cfg, struct rlimit rlimit[], char *file)
 		if (!line)
 			return errno;
 
-		snprintf(line, len, "%s", tty.cmd);
+		snprintf(line, len, "%s", tty.cmd ? tty.cmd : "tty");
 		for (i = 0; i < tty.num; i++) {
 			strlcat(line, " ", len);
 			strlcat(line, tty.args[i], len);