diff --git a/chrome/content/zotero/xpcom/file.js b/chrome/content/zotero/xpcom/file.js
index 629d5101e5..36bd2255d4 100644
--- a/chrome/content/zotero/xpcom/file.js
+++ b/chrome/content/zotero/xpcom/file.js
@@ -77,6 +77,7 @@ Zotero.File = new function(){
 	}
 	
 	function getExtension(file){
+		file = this.pathToFile(file);
 		var pos = file.leafName.lastIndexOf('.');
 		return pos==-1 ? '' : file.leafName.substr(pos+1);
 	}