If a YAML preference has a string instead of the expected format, it'll cause an error - tested with RisExportAdditionalFields and ILLModuleDisclaimerByType but I'm sure others may cause this too. To reproduce: 1) Add 'string' to RisExportAdditionalFields sys pref 2) Visit RIS export link: /cgi-bin/koha/opac-export.pl?op=export&bib=262&format=ris 3) Notice the error Can't use string ("string") as a HASH ref while "strict refs" in use at /kohadevbox/koha/C4/Ris.pm line 132 Not critical, but ideally an error like this should not happen in the event that a system preference has wrong data in it. Adding bug 33431 as "See also" even though it's not the cause of the issue - as the test plans info there may also help here.