diff --git a/chrome/content/zotero/xpcom/mime.js b/chrome/content/zotero/xpcom/mime.js
index 66b87cce29..f972d8d724 100644
--- a/chrome/content/zotero/xpcom/mime.js
+++ b/chrome/content/zotero/xpcom/mime.js
@@ -174,9 +174,7 @@ Zotero.MIME = new function(){
 			
 			case 'image/tif':
 			case 'image/tiff':
-			case 'image/tif':
 			case 'image/x-tif':
-			case 'image/tiff':
 			case 'image/x-tiff':
 			case 'application/tif':
 			case 'application/x-tif':