SQL implicit conversion error

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I have been running v5 and v6 side by side for a while now and v6 has been working with querying nicely, but when i tried running stored procedures today I was running into the following error:

SqlException: Implicit conversion from data type sql_variant to varchar is not allowed. Use the CONVERT function to run this query.

the sproc takes a varchar and an int, and I've been calling it like so:

sproc_name("12345", 67890)

in C# expression I've been highlighting the query and running it, and in v5 it works perfectly and v6 the error above.

is there something different about sprocs in v6?

thanks!

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