Thread:Project:Support desk/File type cannot be uploaded after adding adding to wgFileExtensions

I attempted to enable uploading .pdf documents on my wiki by adding the line  to my local settings. Upon saving, pdf is indeed added to the list of permitted file types in Special:Upload, however when selecting a pdf from the file browser and clicking upload, the upload doesn't start and the permitted filetype line is highlighted in red, as if its saying I attempted to upload an unsupported file type. This happened once before however the problem solved itself without me actually changing anything. Still, rather than just wait, I ought to figure out what's going wrong.


 * Wiki's version page
 * Local settings

Thanks in advance for any help