creation failed: org.xwiki.wiki.manager.WikiManagerException: Failed to create database for wiki

I'm not able to use the "create new wiki" feature. Everytime I try I get the error

Wiki "NAME_OF_NEW_WIKI" creation failed: org.xwiki.wiki.manager.WikiManagerException: Failed to create database for wiki "NAME_OF_NEW_WIKI".

I've tryed with two different installations. Both via the debian/ ubuntu packed manager installed. Everytime with a postgres database.

System1:

• Debian 7 Wheezy
• Postgresql 9.3
• Tomcat 6
• XWiki Enterprise 5.4.2

System1:

• Ubuntu 14.04
• Postgresql 9.3
• Tomcat 7
• XWiki Enterprise 5.4.2