Index: kernel/generic/src/time/clock.c
===================================================================
--- kernel/generic/src/time/clock.c	(revision 6c441cf8f35799043d891a3a77032e1b0e49112b)
+++ kernel/generic/src/time/clock.c	(revision 48eb7a14a8533358b5a3d4be1e99bb2a217817c7)
@@ -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
 		}
 	}