libpngをインストール時にエラー

Calculating dependencies... done!

>>> Emerging (1 of 1) media-libs/libpng-1.2.26-r1 to /
 * libpng-1.2.26.tar.lzma RMD160 ;-) ...                                  [ ok ]
 * libpng-1.2.26.tar.lzma SHA1 ;-) ...                                    [ ok ]
 * libpng-1.2.26.tar.lzma SHA256 ;-) ...                                  [ ok ]
 * libpng-1.2.26.tar.lzma size ;-) ...                                    [ ok ]
 * checking ebuild checksums ;-) ...                                      [ ok ]
 * checking auxfile checksums ;-) ...                                     [ ok ]
 * checking miscfile checksums ;-) ...                                    [ ok ]
 * checking libpng-1.2.26.tar.lzma ;-) ...                                [ ok ]
>>> Unpacking source...
>>> Unpacking libpng-1.2.26.tar.lzma to /var/tmp/portage/media-libs/libpng-1.2.2                                             6-r1/work
unpack libpng-1.2.26.tar.lzma: file format not recognized. Ignoring.
/usr/portage/media-libs/libpng/libpng-1.2.26-r1.ebuild: line 22: cd: /var/tmp/po                                             rtage/media-libs/libpng-1.2.26-r1/work/libpng-1.2.26: No such file or directory
 * Applying libpng-1.2.24-pngconf-setjmp.patch ...

 * Failed Patch: libpng-1.2.24-pngconf-setjmp.patch !
 *  ( /usr/portage/media-libs/libpng/files/libpng-1.2.24-pngconf-setjmp.patch )
 *
 * Include in your bugreport the contents of:
 *
 *   /var/tmp/portage/media-libs/libpng-1.2.26-r1/temp/libpng-1.2.24-pngconf-set                                             jmp.patch-13662.out


!!! ERROR: media-libs/libpng-1.2.26-r1 failed.
Call stack:
  ebuild.sh, line 1614:   Called dyn_unpack
  ebuild.sh, line 751:   Called qa_call 'src_unpack'
  environment, line 3396:   Called src_unpack
  libpng-1.2.26-r1.ebuild, line 23:   Called epatch '/usr/portage/media-libs/lib                                             png/files/libpng-1.2.24-pngconf-setjmp.patch'
  eutils.eclass, line 324:   Called die

!!! Failed Patch: libpng-1.2.24-pngconf-setjmp.patch!
!!! If you need support, post the topmost build error, and the call stack if rel                                             evant.
!!! A complete build log is located at '/var/tmp/portage/media-libs/libpng-1.2.2                                             6-r1/temp/build.log'.