Signup error is shown after creating an administrator account

A fresh new installation of CouchDB comes with no pre defined admin account. Futon shows a little message and provides a Link to fix this.
If I try to add an user named as root and give him a password then Futon will show an error after saving this account.

Signup error: {gen_server,call,
[couch_query_servers,
{get_proc,{doc,<<"_design/_auth">>,

{1, [<<196,79,177,42,38,118,212,129,210,53,82,48, 146,224,206,196>>]}

,
{[

{<<"language">>,<<"javascript">>}

,
{<<"validate_doc_update">>,
<<"\n function(newDoc, oldDoc, userCtx) {\n if (newDoc._deleted === true) {\n // allow deletes by admins and matching users\n // without checking the other fields\n if ((userCtx.roles.indexOf('_admin') !== -1) ||\n (userCtx.name == oldDoc.name))

{\n return;\n }

else {\n throw(

{forbidden: 'Only admins may delete other user docs.'}

);\n }\n }\n\n if ((oldDoc && oldDoc.type !== 'user') || newDoc.type !== 'user') {\n throw(

{forbidden : 'doc.type must be user'}

);\n } // we only allow user docs for now\n\n if (!newDoc.name) {\n throw(

{forbidden: 'doc.name is required'}

);\n }\n\n if (newDoc.roles && !isArray(newDoc.roles)) {\n throw(

{forbidden: 'doc.roles must be an array'}

);\n }\n\n if (newDoc._id !== ('org.couchdb.user:' + newDoc.name)) {\n throw(

{\n forbidden: 'Doc ID must be of the form org.couchdb.user:name'\n }

);\n }\n\n if (oldDoc) { // validate all updates\n if (oldDoc.name !== newDoc.name) {\n throw(

{forbidden: 'Usernames can not be changed.'}

);\n }\n }\n\n if (newDoc.password_sha && !newDoc.salt) {\n throw(

{\n forbidden: 'Users with password_sha must have a salt.' +\n 'See /_utils/script/couch.js for example code.'\n }

);\n }\n\n if (userCtx.roles.indexOf('_admin') === -1) {\n if (oldDoc) { // validate non-admin updates\n if (userCtx.name !== newDoc.name) {\n throw(

{\n forbidden: 'You may only update your own user document.'\n }

);\n }\n // validate role updates\n var oldRoles = oldDoc.roles.sort();\n var newRoles = newDoc.roles.sort();\n\n if (oldRoles.length !== newRoles.length) {\n throw(

{forbidden: 'Only _admin may edit roles'}

);\n }\n\n for (var i = 0; i < oldRoles.length; i++) {\n if (oldRoles[i] !== newRoles[i]) {\n throw(

{forbidden: 'Only _admin may edit roles'}

);\n }\n }\n } else if (newDoc.roles.length > 0) {\n throw(

{forbidden: 'Only _admin may set roles'}

);\n }\n }\n\n // no system roles in users db\n for (var i = 0; i < newDoc.roles.length; i++) {\n if (newDoc.roles[i][0] === '_') {\n throw(

{\n forbidden:\n 'No system roles (starting with underscore) in users db.'\n }

);\n }\n }\n\n // no system names as names\n if (newDoc.name[0] === '_') {\n throw(

{forbidden: 'Username may not start with underscore.'}

);\n }\n }\n">>}]},
[],false,[]},
{<<"_design/_auth">>,
<<"1-c44fb12a2676d481d235523092e0cec4">>}}]}

The admin account will be created and I can log in with the admin account "root". This problem showed up every time I installed CouchDB on my machine.
On Mac OS I used Homebrew ($ brew install couchdb) to install CouchDB which downloads all the sources, compiles them and install properly. On my Linux machine I've followed the compile instructions from the Wiki page.