Index: kernel/generic/src/synch/mutex.c
===================================================================
--- kernel/generic/src/synch/mutex.c	(revision 4c78104a6837166b8f7dd061ec8df30c45dd4c00)
+++ kernel/generic/src/synch/mutex.c	(revision e994898da769c2fefc731de899af8f1370cd52f4)
@@ -66,9 +66,9 @@
 bool mutex_locked(mutex_t *mtx)
 {
-	bool success = semaphore_trydown(&mtx->sem);
-	if (success) {
+	errno_t rc = semaphore_trydown(&mtx->sem);
+	if (rc == EOK) {
 		semaphore_up(&mtx->sem);
 	}
-	return !success;
+	return rc != EOK;
 }