Problem with entity_map of BoundaryMesh

[GerdWachsmuth]

I recently upgraded to FEniCS 2018.1 and encountered a bug. Minimal example:

from dolfin import *

mesh = UnitDiscMesh.create( MPI.comm_world, 5, 1, 2 )
bmesh = BoundaryMesh(mesh, 'exterior')

n = bmesh.num_vertices()


em = [ bmesh.entity_map(0)[i] for i in range(n) ]
print( em )

em = [ bmesh.entity_map(0).array()[i] for i in range(n) ]
print( em )

If I run this snippet, I get

$ python3 bug.py
[61, 62, 90, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89]
[0, 62, 90, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89]

I expected to get the same output twice, but in the second output, the first element is 0.