sass: sass --watch does not detect changes to files in directory

$ sass --version
Sass 3.1.1 (Brainy Betty)
$ ls -la static/
drwxrwxrwx   7 administrator  administrator  238 May 23 11:29 .
drwxr-xr-x  22 administrator  administrator  748 May 23 11:26 ..
drwxrwxrwx   2 administrator  administrator   68 May 19 15:42 coffee
drwxrwxrwx   7 administrator  administrator  238 May 23 11:25 css
drwxrwxrwx   6 administrator  administrator  204 May 23 11:12 img
drwxrwxrwx   2 administrator  administrator   68 May 19 15:42 js
drwxrwxrwx   4 administrator  administrator  136 May 23 11:25 sass
$ sass --watch static/sass:static/css --trace
>>> Sass is watching for changes. Press Ctrl-C to stop.
  overwrite static/css/home.css

SASS detects changes in the directory upon launching, but does not detect changes at runtime. I should note that watching individual files works fine.