diff --git a/sys/kern/kern_umtx.c b/sys/kern/kern_umtx.c
--- a/sys/kern/kern_umtx.c
+++ b/sys/kern/kern_umtx.c
@@ -2612,15 +2612,11 @@
 					umtxq_unbusy_unlocked(&uq->uq_key);
 					continue;
 				}
-				error = 0;
 			}
 		} else if (owner == UMUTEX_RB_NOTRECOV) {
 			error = ENOTRECOVERABLE;
 		}
 
-		if (try != 0)
-			error = EBUSY;
-
 		/*
 		 * If we caught a signal, we have retried and now
 		 * exit immediately.
@@ -2628,6 +2624,19 @@
 		if (error != 0)
 			break;
 
+		/*
+		 * We may have gotten a spurious failure.
+		 */
+		if (owner == UMUTEX_CONTESTED) {
+			umtxq_unbusy_unlocked(&uq->uq_key);
+			continue;
+		}
+
+		if (try != 0) {
+			error = EBUSY;
+			break;
+		}
+
 		umtxq_lock(&uq->uq_key);
 		umtxq_insert(uq);
 		umtxq_unbusy(&uq->uq_key);
@@ -2834,6 +2843,14 @@
 		if (error != 0)
 			break;
 
+		/*
+		 * We may have gotten a spurious failure.
+		 */
+		if (owner == UMUTEX_CONTESTED) {
+			umtxq_unbusy_unlocked(&uq->uq_key);
+			continue;
+		}
+
 		/*
 		 * We set the contested bit, sleep. Otherwise the lock changed
 		 * and we need to retry or we lost a race to the thread