Package: xserver-xorg-core Version: 2:1.16.4-1 Severity: normal xserver-xorg-core depends on one of libegl1-mesa|libegl1 while the virtual package seems to be named libegl1-x11 - which is also the package libegl1-mesa provides. So currently it will lead to problems if an alternative package (like a binary driver) does provide libegl1-x11 but not libegl1.