Pipe dope on my temperature sending unit. Is this okay?

Hi All: The guy who rebuilt my cylinder head installed the brass temperature sending unit into the head with what looks like white pipe dope sealer. Is this correct, or will pipe dope on the sender interfere with the signal that it sends to the temperature gauge in the dash? I thought I read somewhere that these senders should be threaded directly into the head to create a good brass-to-iron connection. My FSM doesn't address this issue. Whaddya think?