mailbox shortcut '^' is unset

[Oliver Graute]

Hello mutt-users,

in my .muttrc I have the following folder-hook:  

# use lower value for reading slower remote IMAP folders         
folder-hook ^imap 'set read_inc=100'                             
# use even lower value for reading even slower remote POP folders
folder-hook ^pop 'set read_inc=1'                                

Since a Ubuntu update from 14.04 to 16.04. It's causing the following
error on mutt startup:

Fehler in /home/oliver/.muttrc, Zeile 11: current mailbox shortcut '^' is unset
Fehler in /home/oliver/.muttrc, Zeile 13: current mailbox shortcut '^' is unset
source: Fehler in /home/oliver/.muttrc

What is wrong with the folder-hook and how to achive same with newer mutt
versions?

currently I have Mutt 1.5.24 (2015-08-30)

Best regards,

Oliver