diff --git a/src/lib/clpb.pl b/src/lib/clpb.pl
index 6ee1b4608..a20694d03 100644
--- a/src/lib/clpb.pl
+++ b/src/lib/clpb.pl
@@ -1251,7 +1251,7 @@
                   node_id(Node, ID) },
                 (   { I0 =:= VI } ->
                     (   { Value =:= 0 } -> { Res = Low }
-                    ;   { Value =:= 1 } -> { Res = High }
+                    ;   { Res = High }
                     )
                 ;   { I0 > VI } -> { Res = Node }
                 ;   state(G0), { get_assoc(ID, G0, Res) } -> []
diff --git a/src/lib/dcgs.pl b/src/lib/dcgs.pl
index 0fa9109ce..4ee763f0f 100644
--- a/src/lib/dcgs.pl
+++ b/src/lib/dcgs.pl
@@ -174,10 +174,10 @@
 dcg_constr(phrase(_,_)). % extension of 7.14.9
 dcg_constr(phrase(_,_,_)). % extension of 7.14.9
 dcg_constr(!). % 7.14.10
-dcg_constr(\+ _) :- % 7.14.11 - not (existence implementation dep.)
-    throw(error(representation_error(dcg_body), phrase/3)).
-dcg_constr((_->_)) :- % 7.14.12 - if-then (existence implementation dep.)
-    throw(error(representation_error(dcg_body), phrase/3)).
+dcg_constr(\+ G_0) :- % 7.14.11 - not (existence implementation def.)
+    throw(error(representation_error(dcg_body), [culprit- (\+ G_0)])).
+dcg_constr((If->Then)) :- % 7.14.12 - if-then (existence implementation def.)
+    throw(error(representation_error(dcg_body), [culprit- (If->Then)])).
 
 % The principal functor of the first argument indicates
 % the construct to be expanded.