--- a/Core/Enumerations.h	Fri Nov 13 15:06:45 2015 +0100
+++ b/Core/Enumerations.h	Tue Nov 17 17:46:32 2015 +0100
@@ -80,6 +80,7 @@
     ErrorCode_DatabasePlugin = 31    /*!< The plugin implementing a custom database back-end does not fulfill the proper interface */,
     ErrorCode_StorageAreaPlugin = 32    /*!< Error in the plugin implementing a custom storage area */,
     ErrorCode_EmptyRequest = 33    /*!< The request is empty */,
+    ErrorCode_NotAcceptable = 34    /*!< Cannot send a response which is acceptable according to the Accept HTTP header */,
     ErrorCode_SQLiteNotOpened = 1000    /*!< SQLite: The database is not opened */,
     ErrorCode_SQLiteAlreadyOpened = 1001    /*!< SQLite: Connection is already open */,
     ErrorCode_SQLiteCannotOpen = 1002    /*!< SQLite: Unable to open the database */,