DbType VarNumeric mapping error

I'm working on a project in .NET 4.0 against an SQL Server 2008 Database. The system uses some legacy code, originally written in .NET 2.0 (converted to 4.0).

Running locally everything works fine, but when I moved the code to the test environment I get the following confusing error from the legacy code:

Exception class: System.ArgumentException No mapping exists from DbType VarNumeric to a known SqlDbType.

I am using the same databse and same user credentails in development and test.

Any pointers?