Martin Luther, painted by Lucas Cranach the Elder, 1529

It’s rare to be invited to an event five years off and even rarer to bicker about its details, but Germany’s Catholic Church finds itself in that delicate situation thanks to an overture from its Protestant neighbors.

German Protestants are planning jubilee celebrations in 2017 to mark the 500th anniversary of Martin Luther’s launching of the Reformation, a major event in the history of Christianity, of Europe and of the German nation, language and culture.

The Protestants have invited the Catholics to join in, a gesture in harmony with the good relations the two halves of German Christianity enjoy and the closeness many believers feel across the denominational divide.

But even after five centuries, being asked to commemorate a divorce that split western Christianity and led to many bloody religious wars is still hard for some Catholics to swallow.

“It’s not impossible in principle, but it depends on the character of the events planned,” Bishop Gerhard Feige, the top Catholic official dealing with Protestants, said in a statement for the Protestant Reformation Day holiday on Wednesday.