| Q | A | ---------------- | ----- | Bug report? | yes | Feature request? | no | BC Break report? | yes | RFC? | no | Symfony version | 3.4.5 issue was introduced by https://github.com/symfony/symfony/commit/c026ec63e33c696c422f3d72c99c8fe64f091376#diff-f7b23d463cba27ac5e4cb677f2be7623R985 results in: https://travis-ci.org/FriendsOfSylius/SyliusImportExportPlugin/jobs/348897843#L923 see also: https://github.com/FriendsOfSylius/SyliusImportExportPlugin/issues/54 quick fix was to simply add a conflict on v3.4.5 https://github.com/FriendsOfSylius/SyliusImportExportPlugin/pull/60 the issue is likely caused by extending the Container class: https://github.com/PolishSymfonyCommunity/SymfonyMockerContainer/blob/master/src/PSS/SymfonyMockerContainer/DependencyInjection/MockerContainer.php#L7