The shortcode is added to the content as a shortcode

I add a shortcode and when I add the shortcode itself to the post I see the shortcode itself and not the shortcode content.

Please help me to fix it.

The original shortcode:

[img]http://snag.gy/8Tn7W.jpg[/img]

The result in the post:

[img]http://snag.gy/mjmRA.jpg[/img]