diff --git a/src/shared/watchdog.c b/src/shared/watchdog.c
index e8184ff661..e4cc0926f7 100644
--- a/src/shared/watchdog.c
+++ b/src/shared/watchdog.c
@@ -133,6 +133,10 @@ static int open_watchdog(void) {
         fn = !watchdog_device || path_equal(watchdog_device, "/dev/watchdog") ?
                 "/dev/watchdog0" : watchdog_device;
 
+        r = free_and_strdup(&watchdog_device, fn);
+        if (r < 0)
+                return log_oom_debug();
+
         watchdog_fd = open(fn, O_WRONLY|O_CLOEXEC);
         if (watchdog_fd < 0)
                 return log_debug_errno(errno, "Failed to open watchdog device %s, ignoring: %m", fn);