diff --git a/xwayland/launcher.c b/xwayland/launcher.c
index 15443cd1..a83784c6 100644
--- a/xwayland/launcher.c
+++ b/xwayland/launcher.c
@@ -165,8 +165,9 @@ create_lockfile(int display, char *lockfile, size_t lsize)
 			return -1;
 		}
 
+		errno = 0;
 		other = strtol(pid, &end, 10);
-		if (end != pid + 10) {
+		if (errno != 0 || end == pid || *end != '\0') {
 			weston_log("can't parse lock file %s\n",
 				lockfile);
 			close(fd);