adding strikeout bbcode, but not working
 

Title: Strikeout
BB Code Tag Name: strikeout
Replacement: {param}
Example: [s]This text has a line through it![/s]
Description: Strikes out selected text.
Use {option}: No
Button Image: N/A
Remove Tag If Empty: Yes
Disable BB Code Within This BB Code: No
Disable Smilies Within This BB Code: No
Disable Word Wrapping Within This BB Code: No

Why isn't it working?