Why emerge tries to replace libvpx 1.7 with 1.6+1.8 in this case? I've asked about this issue on IRC - they help me by recommending to remove "=media-libs/libvpx-1.8.0-r1" from package.keywords, but they was unable to explain reason why emerge tries to install 1.8.0 and downgrade 1.7.0 at first place. So, I've opened this bug to ask for such a reason, because I suspect it may be a bug in emerge. # grep -r libvpx /etc/portage /etc/portage/package.use:www-client/chromium system-libvpx /etc/portage/package.use:# required by www-client/chromium-57.0.2987.133::gentoo[system-libvpx] /etc/portage/package.use:>=media-libs/libvpx-1.5.0 postproc svc /etc/portage/package.keywords:# required by www-client/firefox-65.0.2::gentoo[system-libvpx] /etc/portage/package.keywords:=media-libs/libvpx-1.8.0-r1 ~amd64 /etc/portage/package.keywords:# required by www-client/firefox-65.0.2::gentoo[system-libvpx] /etc/portage/package.keywords:=media-libs/libvpx-1.7.0 ~amd64 # eix libvpx Available versions: 1.5.0(0/3) ~1.6.0-r1(0/4) ~1.6.1(0/4)^t (~)1.7.0(0/5)^t ~1.8.0(0/6)^t (~)1.8.0-r1(0/6)^t {doc +highbitdepth postproc static-libs svc test +threads ABI_MIPS="n32 n64 o32" ABI_PPC="32 64" ABI_S390="32 64" ABI_X86="32 64 x32" CPU_FLAGS_X86="avx avx2 mmx sse sse2 sse3 sse4_1 ssse3"} Installed versions: 1.7.0(0/5)^t(13:03:10 03/09/19)(highbitdepth postproc svc threads -doc -static-libs -test ABI_MIPS="-n32 -n64 -o32" ABI_PPC="-32 -64" ABI_S390="-32 -64" ABI_X86="64 -32 -x32" CPU_FLAGS_X86="avx mmx sse sse2 sse3 sse4_1 ssse3 -avx2") Homepage: https://www.webmproject.org Description: WebM VP8 and VP9 Codec SDK # emerge -uDNav --verbose-conflicts world These are the packages that would be merged, in order: Calculating dependencies... done! [ebuild r UD~] media-libs/libvpx-1.6.1:0/4::gentoo [1.7.0:0/5::gentoo] USE="highbitdepth postproc svc threads -doc -static-libs -test" ABI_X86="(64) -32 (-x32)" CPU_FLAGS_X86="avx mmx sse sse2 sse3 sse4_1 ssse3 -avx2" 1914 KiB [ebuild r U ~] media-libs/libvpx-1.8.0-r1:0/6::gentoo [1.7.0:0/5::gentoo] USE="highbitdepth postproc svc threads -doc -static-libs -test" ABI_X86="(64) -32 (-x32)" CPU_FLAGS_X86="(-avx%*) (-avx2%) (-mmx%*) (-sse%*) (-sse2%*) (-sse3%*) (-sse4_1%*) (-ssse3%*)" 2812 KiB [ebuild U ] app-forensics/rkhunter-1.4.6-r1::gentoo [1.4.6::gentoo] 0 KiB [ebuild U ] app-arch/tar-1.32::gentoo [1.31-r1::gentoo] USE="acl nls (xattr) -minimal (-selinux) -static" 2879 KiB [ebuild U ] sys-power/upower-0.99.9-r1:0/3::gentoo [0.99.8-r1:0/3::gentoo] USE="introspection -doc -ios (-selinux)" 438 KiB [ebuild rR ] media-video/ffmpeg-3.3.6:0/55.57.57::gentoo USE="X alsa bzip2 encode fontconfig gpl hardcoded-tables iconv jpeg2k mp3 network opengl opus postproc sdl theora threads truetype vaapi vdpau vorbis vpx wavpack x264 x265 xcb xvid zlib (-altivec) -amr -amrenc -bluray -bs2b -cdio -chromaprint -chromium -cpudetection -debug -doc -fdk -flite -frei0r -fribidi -gcrypt -gme -gmp -gnutls -gsm -iec61883 -ieee1394 -jack -kvazaar -ladspa -libass -libcaca -libilbc -librtmp -libsoxr -libv4l -lzma (-mipsdspr1) (-mipsdspr2) (-mipsfpu) (-mmal) -modplug -nvenc -openal -openh264 -openssl -oss -pic -pulseaudio -rubberband -samba -snappy -sofalizer -speex -ssh -static-libs -test -twolame -v4l -webp -zeromq -zimg -zvbi" ABI_X86="(64) -32 (-x32)" CPU_FLAGS_X86="aes avx mmx mmxext sse sse2 sse3 sse4_1 sse4_2 ssse3 -3dnow -3dnowext -avx2 -fma3 -fma4 -xop" FFTOOLS="aviocat cws2fws ffescape ffeval ffhash fourcc2pixfmt graph2dot ismindex pktdumper qt-faststart sidxindex trasher" 0 KiB [ebuild U ~] net-im/telegram-desktop-bin-1.6.2::gentoo [1.6.1::gentoo] 46116 KiB [ebuild rR ] dev-qt/qtwebengine-5.11.3:5/5.11::gentoo USE="alsa jumbo-build system-ffmpeg system-icu -bindist -debug -designer -geolocation -pax_kernel -pulseaudio -test -widgets" 0 KiB Total: 8 packages (5 upgrades, 1 downgrade, 2 reinstalls), Size of downloads: 54157 KiB !!! Multiple package instances within a single package slot have been pulled !!! into the dependency graph, resulting in a slot conflict: media-libs/libvpx:0 (media-libs/libvpx-1.8.0-r1:0/6::gentoo, ebuild scheduled for merge) pulled in by (no parents that aren't satisfied by other packages in this slot) (media-libs/libvpx-1.6.1:0/4::gentoo, ebuild scheduled for merge) pulled in by <media-libs/libvpx-1.8 required by (dev-qt/qtwebengine-5.11.3:5/5.11::gentoo, ebuild scheduled for merge) ^ ^^^ (media-libs/libvpx-1.7.0:0/5::gentoo, installed) pulled in by >=media-libs/libvpx-1.7.0:0/5=[postproc] required by (www-client/firefox-66.0.1:0/0::gentoo, installed) ^^ ^^^^^^^^^^ <media-libs/libvpx-1.8:0/5=[postproc] required by (www-client/firefox-66.0.1:0/0::gentoo, installed) ^ ^^^^^^^^ <media-libs/libvpx-1.8 required by (dev-qt/qtwebengine-5.11.3:5/5.11::gentoo, ebuild scheduled for merge) ^ ^^^ (and 2 more with the same problems) NOTE: Use the '--verbose-conflicts' option to display parents omitted above It may be possible to solve this problem by using package.mask to prevent one of those packages from being selected. However, it is also possible that conflicting dependencies exist such that they are impossible to satisfy simultaneously. If such a conflict exists in the dependencies of two different packages, then those packages can not be installed simultaneously. For more information, see MASKED PACKAGES section in the emerge man page or refer to the Gentoo Handbook. The following packages are causing rebuilds: (media-libs/libvpx-1.6.1:0/4::gentoo, ebuild scheduled for merge) causes rebuilds for: (media-video/ffmpeg-3.3.6:0/55.57.57::gentoo, ebuild scheduled for merge) (dev-qt/qtwebengine-5.11.3:5/5.11::gentoo, ebuild scheduled for merge) The following keyword changes are necessary to proceed: (see "package.accept_keywords" in the portage(5) man page for more details) # required by @__auto_slot_operator_replace_installed__ (argument) =media-libs/libvpx-1.6.1 ~amd64 Would you like to add these changes to your config files? [Yes/No]