diff --git a/library/debug.pl b/library/debug.pl
index 9eba79b433..16913782aa 100644
--- a/library/debug.pl
+++ b/library/debug.pl
@@ -382,6 +382,8 @@
 assertion_failed(Reason, G) :-
     prolog:assertion_failed(Reason, G),
     !.
+assertion_failed(unwind(_), _) :-
+    !.
 assertion_failed(Reason, _) :-
     assertion_rethrow(Reason),
     !,