Entity Framework 7 Union Query error

This query works in EF6:

var ids = new int[] { 1, 2, 3 };
var consultants = _dbContext.Times
    .Where(t => ids.Contains(t.MilestoneId))
    .Select(t => t.Consultant)
    .Union(
        _dbContext.TimeBudgets
            .Where(tb => ids.Contains(tb.MilestoneId))
            .Select(tb => tb.Consultant)
     );

In EF7, I get the error:

An unhandled exception occurred while processing the request.