_Originally created by @goupille on [#11735 (Redmine)](https://public-redmine-archive.tails.boum.org/code/issues/11735)_ there were multiple reports about tails-upgrader crashing with this error : Error message stating "cannot chose a download server" "This should not happen. Please report a bug" The following is copied from terminal: Prototype mismatch: sub Tails::MirrorPool::assert ($;$) vs none at /usr/share/perl5/Tails/MirrorPool.pm line 28. Prototype mismatch: sub Tails::IUK::Frontend::assert ($;$) vs none at /usr/share/perl5/Tails/IUK/Frontend.pm line 42. This version of Tails is outdated, and may have security issues. Upgrade available <b>You should upgrade to Tails 2.5.</b> For more information about this new version, go to https://tails.boum.org/news/version_2.5/ It is recommended to close all the open applications during the upgrade. Downloading the upgrade might take a long time, from several minutes to a few hours. The networking will be disabled after downloading the upgrade. Download size: 324.66MiB Do you want to upgrade now?: Upgrade now / Upgrade later ** (zenity:5402): WARNING **: Couldn't register with accessibility bus: Did not receive a reply. Possible causes include: the remote application did not send a reply, the message bus security policy blocked the reply, the reply timeout expired, or the network connection was broken. Gtk-Message: GtkDialog mapped without a transient parent. This is discouraged. Downloading the upgrade to Tails 2.5... undefined:183 }, ^ SyntaxError: Unexpected token } at Object.parse (native) at Object.<anonymous> (/usr/local/bin/tails-transform-mirror-url:22:8) at Module._compile (module.js:456:26) at Object.Module._extensions..js (module.js:474:10) at Module.load (module.js:356:32) at Function.Module._load (module.js:312:12) at Function.Module.runMain (module.js:497:10) at startup (node.js:119:16) at node.js:906:3 Error while choosing a download server <b>Could not choose a download server.</b> This should not happen. Please report a bug. ** (zenity:5409): WARNING **: Couldn't register with accessibility bus: Did not receive a reply. Possible causes include: the remote application did not send a reply, the message bus security policy blocked the reply, the reply timeout expired, or the network connection was broken. Gtk-Message: GtkDialog mapped without a transient parent. This is discouraged. Error while choosing a download server <b>Could not choose a download server.</b> This should not happen. Please report a bug. "tails-transform-mirror-url" unexpectedly returned exit value 8 at /usr/share/perl5/Tails/MirrorPool.pm line 82. at /usr/share/perl5/Tails/IUK/Frontend.pm line 593. Feature Branch: bugfix/11735-mirror-pool-size, mirror-pool-dispatcher:bugfix/11735-mirror-pool-size ### Related issues - **Blocks** tails/tails#12405