Thumbnails not showing in file-list view

Steps to reproduce
1. In the 'Files' App go to a folder with pictures.
2. In the list are only the standard icons for pictures and not the thumbnails, which I had in earlier versions of OC.

Expected behaviour
See the thumbnails to the left of the file name.

Actual behaviour
Only standard icon is shown.

Server configuration
Operating system: Debian 8.7
Web server: Apache 2.4.10
Database: MySQL 5.5.54
PHP version: 5.6.29
ownCloud version (see ownCloud admin page):
Updated from an older ownCloud or fresh install: Updated
Special configuration (external storage, external authentication, reverse proxy, server-side-encryption): No

Integrity status for oC9+

Login as admin user into your ownCloud and access
paste the results here.

No errors have been found.

Preview is enabled in the config.php. All other kind of previews and normal views with the gallary app are working without problems. It is just, that there are not thumbnails shown, when I am looking at the files as listing. Has been working always before.

Best regards,


if something stopped working after an upgrade which worked before (and without any sign in the release notes that its behavior changed) then please always report a new bug to the bugtracker at

Well, I would have probably done that, if I could clearly recap the way I was comming from. Unfortunately I did not do excessive test between the steps. I wanted to move to a different server and wanted to use the most actual version. So I completed 3 update steps comming from 8.1.11. I just checked functionality by a quick login and went on updating to the next version.


Problem solved:

As I wanted to debug further, I found in the documentation that the debug value in the config.php should be set to 'debug' => true.

That made me thinking, because the value is without quotation marks. I could swear, I've had boolean values set in my config.php not by me with quotation marks. E. g. 'versions' => 'true'. There I had also set 'enable_previews' => 'true' with quotation marks.

Now leaving quotation marks away solved my problem. However, if I set a wrong value in the config.php, which does not lead to the expected result, shouldn't there be a warning in the log and then should fall back to the default? Which I think in the case of enable_preview would be true.

Even though it was obviously my mistake the handling of Owncloud with unclear of invalid values in the config.php was not really helpful in this case.


Feel free to create a bugreport about the handling of this values at: