This seems to be breakage from bug 13813. This needs to be fixed and also covered with a test to avoid further breakage.
Created attachment 15090 [details] patches for 4.10
Created attachment 15091 [details] patches for 4.9
Re-assigning to Karolin for inclusion in 4.10.next, 4.9.next.
Pushed to autobuild-v4-{10,9}-test.
(In reply to Karolin Seeger from comment #4) Pushed to both branches. Closing out bug report. Thanks!