Can't validate boolean

[mcesaro]

Hi, I'm trying to validate a boolean input like this:

liver:validate([{<<"test">>, [string, is_boolean]}], [{<<"test">>, <<"false">>}]).
liver:validate([{<<"test">>, [string, is_boolean]}], [{<<"test">>, 1}])
liver:validate([{<<"test">>, [string, is_boolean]}], [{<<"test">>, <<"0">>}]).
liver:validate([{<<"test">>, [string, is_boolean]}], [{<<"test">>, <<"false">>}], [{strict, true}]).
liver:validate([{<<"test">>, [string, is_boolean]}], [{<<"test">>, <<"off">>}], [{strict, true}]).

but the result is invariably:

{error,[{<<"test">>,not_boolean}]}

Am I doing something wrong?