Unable to make a query and display information ("Bad request") with GraphDB triple store

[RdNetwork]

Note: this only happens with current versions, not the releases found at http://wifo5-03.informatik.uni-mannheim.de/pubby/ )

I have a working SPARQL Endpoint managed using GraphDB deployed locally. I want to use pubby to display all the linked data available in this endpoint. I used Pubby 0.3.3, and it was working fine (using this configuration file: http://pastebin.com/s0qYPptQ ) but I was bothered by the fact that anonymous nodes were not displayed, except for their quantity. As it seemed that this was fixed in future versions, I decided to build pubby 0.4 from the source code available here. After fixing some deployment errors (such as deleting non-working tests and non-working Javadoc generation) I managed to get a working deployment... only to see this message displayed on pubby's webpage:

Configuration error

Pubby failed to properly initialize. This is probably due to an error in the configuration file. The message was:

Error parsing configuration file <file:/var/lib/tomcat8/webapps/pubby_seecr/WEB-INF/config.ttl>: Error making the query, see cause for details 

I used the same configuration file, since I could not see any kind of difference between 0.3.3's config files and 0.4's. So I checked GraphDB's log, and they say this:

[INFO ] 2016-07-15 14:21:10,137 [repositories/BIO | o.o.h.s.r.s.StatementsController] GET statements
[INFO ] 2016-07-15 14:21:10,139 [repositories/BIO | o.o.h.s.ProtocolExceptionResolver] Client sent bad request ( 406)
org.openrdf.http.server.ClientHTTPException: No acceptable file format found.
        at org.openrdf.http.server.ProtocolUtil.getAcceptableService(ProtocolUtil.java:190)
        at org.openrdf.http.server.repository.statements.StatementsController.getExportStatementsResult(StatementsController.java:348)
        at org.openrdf.http.server.repository.statements.StatementsController.handleRequestInternal(StatementsController.java:113)
[...]

This error usually happens if the types described in the "Accept:" field of the GET request are wrong or empty, but checking with tcpdump I noticed that they weren't wrong at all.

So I'm not sure what to do and especially why this only happens with the most recent versions.

Any clue? Thanks :)