sql server - Entity Framework 4 inheritance issue when deployed -

i have asp.net page using ef 4,

it has couple of tables linked using inheritance relationship. locally when running on asp.net development server works fine, when deploy iis (windows server 2003) i'm getting error:

the resulttype of specified expression not compatible required type.  expression resulttype 'transient.reference[a]' required type  'transient.reference[b]' 

where : b

i have found https://connect.microsoft.com/visualstudio/feedback/details/544639/ef4-inheritance-defined-using-queryview-doesnt-work-properly-with-association

but doesn't explain why works on development server (though have .net 4.5 installed, development server says it's running on 4.0) , why class/table has problem.

i have other tables have same kind of relationships , code works fine.

i can't paste code, in ef i'm doing like:

var bs = repository.a.oftype<b>().include(..).tolist();