Hi! On a stable system, with the following apt priorities: stable=500 testing=333 unstable=250 experimental=200 I requested aptitude to upgrade a package, let's call it "foo", to the version in testing. It depends on libc6 (and libc6 has -dev, locales and so on, but these come together). Aptitude proposed the following solutions, in order: 1. remove foo 2. keep foo at current version (stable) 3. install glibc/experimental 4. install glibc/unstable 5. install glibc/testing The obviously correct one is 5. Solutions 1 and 2 shouldn't even be considered as they are not solutions to what aptitude was invoked to do -- but that's a separate issue. What I'm reporting here is the order of 3, 4, and 5. Aptitude seems to sort available versions to prefer newest first, ignoring configured releases -- as opposed to obeying the priority as it does during the initial resolution. Proposed fix: prefix the versions with priority? Meow! -- Package-specific info: Terminal: xterm-256color $DISPLAY not set. which aptitude: /usr/bin/aptitude aptitude version information: aptitude 0.8.13 Compiler: g++ 10.2.1 20210110 Compiled against: apt version 6.0.0 NCurses version 6.2 libsigc++ version: 2.10.4 Gtk+ support disabled. Qt support disabled. Current library versions: NCurses version: ncurses 6.2.20201114 cwidget version: 0.5.18 Apt version: 6.0.0 aptitude linkage: linux-vdso.so.1 (0x00007ffca27b0000) libapt-pkg.so.6.0 => /usr/lib/x86_64-linux-gnu/libapt-pkg.so.6.0 (0x00007fb9324ae000) libncursesw.so.6 => /lib/x86_64-linux-gnu/libncursesw.so.6 (0x00007fb932473000) libtinfo.so.6 => /lib/x86_64-linux-gnu/libtinfo.so.6 (0x00007fb932444000) libsigc-2.0.so.0 => /usr/lib/x86_64-linux-gnu/libsigc-2.0.so.0 (0x00007fb93243b000) libcwidget.so.4 => /usr/lib/x86_64-linux-gnu/libcwidget.so.4 (0x00007fb932335000) libsqlite3.so.0 => /usr/lib/x86_64-linux-gnu/libsqlite3.so.0 (0x00007fb9321f2000) libboost_iostreams.so.1.74.0 => /usr/lib/x86_64-linux-gnu/libboost_iostreams.so.1.74.0 (0x00007fb9321d7000) libxapian.so.30 => /usr/lib/x86_64-linux-gnu/libxapian.so.30 (0x00007fb931fb5000) libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0 (0x00007fb931f93000) libstdc++.so.6 => /usr/lib/x86_64-linux-gnu/libstdc++.so.6 (0x00007fb931dc6000) libm.so.6 => /lib/x86_64-linux-gnu/libm.so.6 (0x00007fb931c82000) libgcc_s.so.1 => /lib/x86_64-linux-gnu/libgcc_s.so.1 (0x00007fb931c68000) libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007fb931aa1000) libresolv.so.2 => /lib/x86_64-linux-gnu/libresolv.so.2 (0x00007fb931a87000) libz.so.1 => /lib/x86_64-linux-gnu/libz.so.1 (0x00007fb931a6a000) libbz2.so.1.0 => /lib/x86_64-linux-gnu/libbz2.so.1.0 (0x00007fb931a57000) liblzma.so.5 => /lib/x86_64-linux-gnu/liblzma.so.5 (0x00007fb931a2f000) liblz4.so.1 => /usr/lib/x86_64-linux-gnu/liblz4.so.1 (0x00007fb931a0c000) libzstd.so.1 => /usr/lib/x86_64-linux-gnu/libzstd.so.1 (0x00007fb93192f000) libudev.so.1 => /usr/lib/x86_64-linux-gnu/libudev.so.1 (0x00007fb931907000) libsystemd.so.0 => /lib/x86_64-linux-gnu/libsystemd.so.0 (0x00007fb93185f000) libgcrypt.so.20 => /usr/lib/x86_64-linux-gnu/libgcrypt.so.20 (0x00007fb93173f000) libxxhash.so.0 => /usr/lib/x86_64-linux-gnu/libxxhash.so.0 (0x00007fb931726000) /lib64/ld-linux-x86-64.so.2 (0x00007fb932ace000) libdl.so.2 => /lib/x86_64-linux-gnu/libdl.so.2 (0x00007fb931720000) librt.so.1 => /lib/x86_64-linux-gnu/librt.so.1 (0x00007fb931713000) libuuid.so.1 => /usr/lib/x86_64-linux-gnu/libuuid.so.1 (0x00007fb93170a000) libcap.so.2 => /lib/x86_64-linux-gnu/libcap.so.2 (0x00007fb9316ff000) libgpg-error.so.0 => /lib/x86_64-linux-gnu/libgpg-error.so.0 (0x00007fb9316d9000)