204 response not working in /clear endpoint

After a file is unregistered from the background knowledge, any repitition of same request yields the following result:

(500 internal server error) goal unexpectedly failed: web_api:clear_bg([protocol(http),peer(ip(127,0,0,1)),pool(client('httpd@4444',web_api:http_dispatch,<stream>(0x7fe91c0310c0),<stream>(0x7fe91c0117b0))),input(<stream>(0x7fe91c0310c0)),method(post),request_uri('/clear'),path('/clear'),http_version(1-1),accept_encoding('gzip,deflate'),content_type('application/json'),content_length(274),host(localhost),port(4444),connection('Keep-Alive'),user_agent('Apache-HttpClient/4.1.1 (java 1.5)')])