diff --git a/plugins/squirrelmail_usercopy/squirrelmail_usercopy.php b/plugins/squirrelmail_usercopy/squirrelmail_usercopy.php
index 12fd5b542..89db8eb5b 100644
--- a/plugins/squirrelmail_usercopy/squirrelmail_usercopy.php
+++ b/plugins/squirrelmail_usercopy/squirrelmail_usercopy.php
@@ -255,6 +255,6 @@ class squirrelmail_usercopy extends rcube_plugin
             return utf8_encode($sig);
         }
 
-        return rcube_charset::convert($str, $charset, RCMAIL_CHARSET);
+        return rcube_charset::convert($str, $charset, RCUBE_CHARSET);
     }
 }