Index: sys/kern/kern_timeout.c
===================================================================
--- sys/kern/kern_timeout.c
+++ sys/kern/kern_timeout.c
@@ -1209,7 +1209,7 @@
 		 */
 		c->c_iflags &= ~CALLOUT_PENDING;
 		c->c_flags &= ~CALLOUT_ACTIVE;
-		not_on_a_list = 1;
+		not_on_a_list = -1;
 	} else {
 		not_on_a_list = 0;
 	}
@@ -1372,7 +1372,7 @@
 				cc_exec_drain(cc, direct) = drain;
 			}
 			CC_UNLOCK(cc);
-			return (0);
+			return (not_on_a_list);
 		}
 		CTR3(KTR_CALLOUT, "failed to stop %p func %p arg %p",
 		    c, c->c_func, c->c_arg);
@@ -1381,7 +1381,7 @@
 		}
 		CC_UNLOCK(cc);
 		KASSERT(!sq_locked, ("sleepqueue chain still locked"));
-		return (0);
+		return (not_on_a_list);
 	}
 	if (sq_locked)
 		sleepq_release(&cc_exec_waiting(cc, direct));