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I have a number field U for which I consider its automorphisms through Hom(U,U). The identity one=Hom(U,U).identity() behaves weirdly under right multiplication:

U = CyclotomicField(3)
f = Hom(U,U)[1]
print f
print "--------------------"
one = Hom(U,U).identity()
print f*one
print "--------------------"
print one*f
print "--------------------"
print f*f

When I run this code, I expect f to be printed thrice, followed by the identity morphism. However, while the first and third output do in fact both print f, the second prints

Composite map:
  From: Cyclotomic Field of order 3 and degree 2
  To:   Cyclotomic Field of order 3 and degree 2
  Defn:   Identity endomorphism of Cyclotomic Field of order 3 and degree 2
        then
          Ring endomorphism of Cyclotomic Field of order 3 and degree 2
          Defn: zeta3 |--> -zeta3 - 1

Is this a bug or is this this behaviour explained somewhere in the documentation?