diff --git a/src/udev/udevd.c b/src/udev/udevd.c
index 27caaf14a0..339e9c4570 100644
--- a/src/udev/udevd.c
+++ b/src/udev/udevd.c
@@ -615,6 +615,7 @@ static void worker_returned(int fd_worker) {
                 ssize_t size;
                 struct ucred *ucred = NULL;
                 struct udev_list_node *loop;
+                bool found = false;
 
                 size = recvmsg(fd_worker, &msghdr, MSG_DONTWAIT);
                 if (size < 0) {
@@ -646,6 +647,8 @@ static void worker_returned(int fd_worker) {
 
                         if (worker->pid != ucred->pid)
                                 continue;
+                        else
+                                found = true;
 
                         /* worker returned */
                         if (worker->event) {
@@ -658,6 +661,9 @@ static void worker_returned(int fd_worker) {
                         worker_unref(worker);
                         break;
                 }
+
+                if (!found)
+                        log_warning("unknown worker ["PID_FMT"] returned", ucred->pid);
         }
 }