Changing start number does not avoid cached copy of previously syled code content

If I change the start number (and nothing else) on an update to existing content, the cached copy of the content is retrieved and the new start number is not enforced.

This is due (apparently) to a simple error in the cache key for previously filtered content.
in geshifilter.pages.inc:
$cache_id = "geshifilter:$lang:$line_numbering:$line_numbering:$inline_mode" . md5($title . $source_code);
should be:
$cache_id = "geshifilter:$lang:$line_numbering:$linenumbers_start:$inline_mode" . md5($title . $source_code);

Patch attached.