Rails 3.2.12 File Icons Incorrect

There is a file icon glitch with the types of files being uploaded to the app. For example, a file with a ".xlsx" extension appears with a word icon instead of an excel icon.

I made the update as seen below, but to no avail. Any thoughts on where else I should be looking?

li.page {
  background-position: 0 1px;
  background-repeat: no-repeat;
  padding-left: 20px;
}

li.default {
  background-image: url(page_green.png);
}

li.xls {
  background-image: url(page_excel.png);
}

li.xlsx {
  background-image: url(page_excel.png);
}

li.doc {
  background-image: url(page_word.png);
}

li.docx {
  background-image: url(page_word.png);
}`