increasing the file limit of montage

Question

montage -list resource says that the file limit is 768. I'd like to change that to, say, 10001. To facilitate this I edited vim /etc/ImageMagick-6/policy.xml, changing this line:

<!-- <policy domain="resource" name="file" value="10001"/> -->

To this:

<policy domain="resource" name="file" value="10001"/>

But when I rerun montage -list resource it still says that the file limit is 768.

Any ideas?