diff --git a/src/lib/iso_ext.pl b/src/lib/iso_ext.pl
index a53ac991..d53ff47b 100644
--- a/src/lib/iso_ext.pl
+++ b/src/lib/iso_ext.pl
@@ -359,10 +359,10 @@ call_nth_nesting(C, ID) :-
     bb_put(ID, 0),
     bb_put(i_call_nth_counter, C).
 
-%% countall(Goal, N).
+%% countall(G_0, N).
 %
-% countall(Goal, N) counts all solutions of Goal and unifies N with
-% this number of solutions. This predicate always succeeds once.
+% countall(G_0, N) is true iff N unifies with the total number of
+% answers of call(G_0).
 
 :- meta_predicate(countall(0, ?)).
 
@@ -371,7 +371,7 @@ countall(Goal, N) :-
     (   integer(N) ->
         (   N < 0 ->
             domain_error(not_less_than_zero, N, countall/2)
-        ;   N > 0
+        ;   true
         )
     ;   true
     ),