glyphicon-cog display something else

[Soraph]

As shown in the image below, when asking bootstrap to display the glyphicon-cog I get
another symbol.

Here the repo where I'm testing it: Soraph/treebook@c1007f6

[cvrebert]

Works fine in both v3.0.0 and master. Must be some deployment issue with your project.
Perhaps you're mixing files from different versions of Bootstrap? Could be related to #10778.

[Soraph]

I'm not mixing versions and I don't have any interfering CSS rule or script and the code is not minified, I tried using the glyphs from dca7be6 and the bootstrap.css from f19126e but nothing change. The problem is present on chrome 30.0.1599.66 and firefox 24.0.

I hope it will help.

EDIT:
Found the issue, is not related to bootstrap, is a bug in rails, thank you for your time and patience!