xsd:decimal parsed as xsd:double

[giacomociti]

the following

@prefix log: <http://www.w3.org/2000/10/swap/log#> .
@prefix xsd: <http://www.w3.org/2001/XMLSchema#> .
@prefix : <http://www.example.org/> .

:foo :bar "10.5"^^xsd:decimal .

{
    :foo :bar ?value .
    ([] ?datatype) log:dtlit ?value
}
=>
{
    :foo  :type ?datatype
} .

derives :foo :type xsd:double. Is it on purpose or it's a bug?