Praise be to Allaah.
We put this question to Shaykh Muhammad ibn Saalih al-Uthaymeen, who replied as follows:
Does the other partner agree to that? If he or she agrees to it, then there is nothing wrong with it, but if he or she does not agree to it, then it is not permissible.
And Allaah knows best.
Sheikh Muhammed Salih Al-Munajjid