Multiple Executions of Programmes from /etc/mailcap fail

Binary package hint: firefox

On my system Firefox reads mime type assocations from /etc/mailcap. After having launched a programme once and opening a file of that mime-type again, the programme doesn't appear in the dialogue again. However, when inserting the programme into ~/.mailcap it always works.

$ cat /etc/mailcap
[...]
text/plain; less '%s'; needsterminal
text/html; /usr/bin/sensible-browser '%s'; description=HTML Text; nametemplate=%s.html
application/pdf; /usr/bin/xpdf '%s'; test=test "$DISPLAY" != ""; description=Portable Document Format; nametemplate=%s.pdf
application/x-pdf; /usr/bin/xpdf '%s'; test=test "$DISPLAY" != ""; description=Portable Document Format; nametemplate=%s.pdf
application/x-troff-man; /usr/bin/nroff -mandoc -Tutf8; copiousoutput; print=/usr/bin/nroff -mandoc -Tutf8 | print text/plain:-
message/rfc822; mutt -Rf '%s'; edit=mutt -f '%s'; needsterminal
application/x-tar; /bin/tar tvf -; print=/bin/tar tvf - | print text/plain:-; copiousoutput
application/x-gtar; /bin/tar tvzf -; print=/bin/tar tvzf - | print text/plain:-; copiousoutput
application/x-dvi; /usr/bin/xdvi '%s'; description=TeX DVI; test=test -n "$DISPLAY"; nametemplate=%s.dvi
text/plain; more '%s'; needsterminal
text/plain; view '%s'; edit=vim '%s'; compose=vim '%s'; needsterminal
text/html; /usr/bin/w3m -T text/html '%s'; needsterminal; description=HTML Text; nametemplate=%s.html
text/html; /usr/bin/w3m -dump -T text/html '%s'; copiousoutput; description=HTML Text; nametemplate=%s.html
text/*; less '%s'; needsterminal
text/*; view '%s'; edit=vim '%s'; compose=vim '%s'; needsterminal
text/*; more '%s'; needsterminal
application/x-debian-package; /usr/lib/mime/debian-view '%s'; needsterminal; description=Debian GNU/Linux Package; nametemplate=%s.deb
audio/basic; /usr/lib/mime/playaudio '%s'; description=Basic uLaw Audio; nametemplate=%s.au
[...]

$ cat .mailcap
application/pdf; xpdf %s