Why can't I install multiple both x86 and x86_64 versions of a library side by side?

Edited output: # apt-get install librados2:amd64 librados2:i386 The following packages have unmet dependencies: librados2:amd64 : Conflicts: librados2 but 0.80.7-2+deb8u1 is to be installed librados2 : Conflicts: librados2:amd64 but 0.80.7-2+deb8u1 is to be installed E: Unable to correct problems, you have held broken packages. # apt-cache show librados2:amd64=0.80.7-2+deb8u1 librados2:i386=0.80.7-2+deb8u1 Package: librados2 Version: 0.80.7-2+deb8u1 Architecture: amd64 Replaces: libcrush, libcrush1, librados, librados1 Depends: libboost-system1.55.0, libboost-thread1.55.0, libc6 (>= 2.14), libgcc1 (>= 1:4.1.1), libnspr4 (>= 2:4.9-2~) | libnspr4-0d (>= 1.8.0.10), libnss3 (>= 2:3.13.4-2~) | libnss3-1d (>= 3.12.0~1.9b1), libstdc++6 (>= 4.9), libuuid1 (>= 2.16) Pre-Depends: multiarch-support Conflicts: libcrush, libcrush1, librados, librados1 Tag: role::shared-lib Section: libs Package: librados2 Version: 0.80.7-2+deb8u1 Architecture: i386 Replaces: libcrush, libcrush1, librados, librados1 Depends: libboost-system1.55.0, libboost-thread1.55.0, libc6 (>= 2.9), libgcc1 (>= 1:4.1.1), libnspr4 (>= 2:4.9-2~) | libnspr4-0d (>= 1.8.0.10), libnss3 (>= 2:3.13.4-2~) | libnss3-1d (>= 3.12.0~1.9b1), libstdc++6 (>= 4.9), libuuid1 (>= 2.16) Pre-Depends: multiarch-support Conflicts: libcrush, libcrush1, librados, librados1 Tag: role::shared-lib Section: libs Why Conflicts:? I don't see this library in conflict list displayed by apt-cache info (there is librados**1**, not librados**2**)... What prevents having librados2:i386 in /usr/lib/i386-linux-gnu/librados.so.2.0.0 and librados2:amd64 in /usr/lib/x86_64-linux-gnu/librados.so.2.0.0?