Calvin "prayed to" and "revered" the dead

I was amazed to see this in Calvin:

“O Philip Melanchthon! for I appeal to you who live in the presence of God with Christ, and wait for us there until we are united with you in blessed rest.” (LCC, Calvin’s Theological Treatises, ‘The clear explanation … concerning the true partaking of … the Holy Supper’, p258)

Though in fact Calvin seems to be appealing more to Melanchthon’s writings, but it is still striking that he should address a dead man like this, even if only for a rhetorical flourish.

On p265 Calvin adds that Tileman Heshusius should “revere as sacred” the memory of Philip Melanchthon.