diff --git a/chrome/content/zotero/xpcom/attachments.js b/chrome/content/zotero/xpcom/attachments.js
index 183810054..a30bd0f3a 100644
--- a/chrome/content/zotero/xpcom/attachments.js
+++ b/chrome/content/zotero/xpcom/attachments.js
@@ -1373,7 +1373,7 @@ Zotero.Attachments = new function(){
 			var win = doc.defaultView;
 			if(win) {
 				win = win.wrappedJSObject;
-				if(win && "PDFJS" in win && win.PDFJS.isFirefoxExtension) {
+				if(win && "PDFJS" in win) {
 					return true;
 				}
 			}