Index: kernel/generic/src/time/clock.c
===================================================================
--- kernel/generic/src/time/clock.c	(revision 83512f218dedeb9823a83908ea76dbed9da915bd)
+++ kernel/generic/src/time/clock.c	(revision e55571317c3b62308d58f97fb8f2aa78c6fd7aa4)
@@ -191,4 +191,12 @@
 		if (!ticks && !PREEMPTION_DISABLED) {
 			scheduler();
+#ifdef CONFIG_UDEBUG
+			/*
+			 * Give udebug chance to stop the thread
+			 * before it begins executing.
+			 */
+			if (istate_from_uspace(THREAD->udebug.uspace_state))
+				udebug_before_thread_runs();
+#endif
 		}
 	}