When executing Queries with parameters on the same table, I get the error:
Npgsql.PostgresException: 42804: Column »bool1« has Type boolean but expression has type integer

But when debugging the datatype of the NpgsqlParameter is correct, directly before I call ExecuteNonQuery()

I attached a little test project, that reproduces this error.
Only the connection string inside has to be adjustet.
It creates a new database, a new table and first tries to update a row (which is not still there) and as it couldn't update the row it creates it.
During the creation of this row the Exception is thrown.

NpgsqlTest.zip