diff --git a/lang/en_utf8/error.php b/lang/en_utf8/error.php
index 41a265a398e..cd67f105fe6 100644
--- a/lang/en_utf8/error.php
+++ b/lang/en_utf8/error.php
@@ -53,6 +53,7 @@ $string['sessionerroruser2'] = 'A server error that affects your login session w
 $string['sessionipnomatch'] = 'Sorry, but your IP number seems to have changed from when you first logged in.  This security feature prevents crackers stealing your identity while logged in to this site.  Normal users should not be seeing this message - please ask the site administrator for help.';
 $string['statscatchupmode'] = 'Statistics is currently in catchup mode. So far $a->daysdone day(s) have been processed and $a->dayspending are pending. Check back soon!';
 $string['unknowncourse'] = 'Unknown course named \"$a\"';
+$string['unknownuseraction'] = 'Sorry, I do not understand this user action.';
 $string['usernotaddederror'] = 'User \"$a\" not added - unknown error';
 $string['usernotaddedregistered'] = 'User \"$a\" not added - already registered';
 $string['usernotavailable'] = 'The details of this user are not available to you.';