SqlException: An expression of non-boolean type specified in a context where a condition is expected, near ')'

This is the query I am trying to run against EF7

_context.Event.Where(e => e.Invitations.Any(i => i.User.Id == currentUserId));

Fairly simple query indeed and I can't see any non-boolean phrase passed as a condition.

Event here is in a one-to-many relationship with Invitation.