strange accidentals

[Karl Hammar]

How do I remove the unwanted explicit flats in the next to last
measure in:

\version "2.4.2"

\relative c'' {
  \override Score.BarNumber  #'break-visibility = #end-of-line-invisible
  \mark #03
  \clef treble
  \key c \minor
  a2 b |
  d1 |
  \mark #04
  \set Score.currentBarNumber = #1
  d2 es8. as,16 bes8 c |
%         ^     ^ unwanted explicit flats here
  d1
}

Regards
/Karl