diff --git a/library/prolog_clause.pl b/library/prolog_clause.pl
index 173c78e558..b99559a8fc 100644
--- a/library/prolog_clause.pl
+++ b/library/prolog_clause.pl
@@ -400,7 +400,7 @@
     ).
 unify_clause((Head => Body), Compiled1, Module, TermPos0, TermPos) :-
     !,
-    unify_clause2(Head :- Body, Compiled1, Module, TermPos0, TermPos).
+    unify_clause2((Head :- Body), Compiled1, Module, TermPos0, TermPos).
 unify_clause(Read, Decompiled, Module, TermPos0, TermPos) :-
     unify_clause2(Read, Decompiled, Module, TermPos0, TermPos).