Bitcoind importprivkey Error Code -4 ubuntu

[RandomQ]

Trying to track down some info about this error code.
I'm getting Error Code -4 while using bitcoind 60200 trying to importprivkey.
I tried to search and couldn't find anything that seems to be related to this error.

error: {"code":-4,"message":"Error adding key to wallet"}

thanks for any help

[Pieter Wuille]

Maybe the key is already in the wallet?