diff --git a/chrome/content/zotero/xpcom/collectionTreeView.js b/chrome/content/zotero/xpcom/collectionTreeView.js
index a2c97b959..19184ce71 100644
--- a/chrome/content/zotero/xpcom/collectionTreeView.js
+++ b/chrome/content/zotero/xpcom/collectionTreeView.js
@@ -2188,9 +2188,7 @@ Zotero.CollectionTreeView.prototype.drop = Zotero.Promise.coroutine(function* (r
 				}
 				*/
 				
-				let wm = Components.classes["@mozilla.org/appshell/window-mediator;1"]
-						   .getService(Components.interfaces.nsIWindowMediator);
-				let lastWin = wm.getMostRecentWindow("navigator:browser");
+				let lastWin = Services.wm.getMostRecentWindow("navigator:browser");
 				lastWin.openDialog('chrome://zotero/content/merge.xul', '', 'chrome,modal,centerscreen', io);
 				
 				yield Zotero.DB.executeTransaction(function* () {
@@ -2244,9 +2242,7 @@ Zotero.CollectionTreeView.prototype.drop = Zotero.Promise.coroutine(function* (r
 				var url = data[i];
 				
 				if (url.indexOf('file:///') == 0) {
-					var wm = Components.classes["@mozilla.org/appshell/window-mediator;1"]
-							   .getService(Components.interfaces.nsIWindowMediator);
-					var win = wm.getMostRecentWindow("navigator:browser");
+					let win = Services.wm.getMostRecentWindow("navigator:browser");
 					// If dragging currently loaded page, only convert to
 					// file if not an HTML document
 					if (win.content.location.href != url ||
@@ -2264,9 +2260,7 @@ Zotero.CollectionTreeView.prototype.drop = Zotero.Promise.coroutine(function* (r
 				
 				// Still string, so remote URL
 				if (typeof file == 'string') {
-					var wm = Components.classes["@mozilla.org/appshell/window-mediator;1"]
-							   .getService(Components.interfaces.nsIWindowMediator);
-					var win = wm.getMostRecentWindow("navigator:browser");
+					let win = Services.wm.getMostRecentWindow("navigator:browser");
 					win.ZoteroPane.addItemFromURL(url, 'temporaryPDFHack', null, row); // TODO: don't do this
 					continue;
 				}
diff --git a/chrome/content/zotero/xpcom/itemTreeView.js b/chrome/content/zotero/xpcom/itemTreeView.js
index 032e408cb..80aff7a6e 100644
--- a/chrome/content/zotero/xpcom/itemTreeView.js
+++ b/chrome/content/zotero/xpcom/itemTreeView.js
@@ -3211,9 +3211,7 @@ Zotero.ItemTreeView.prototype.drop = Zotero.Promise.coroutine(function* (row, or
 	else if (dataType == 'text/x-moz-url' || dataType == 'application/x-moz-file') {
 		// Disallow drop into read-only libraries
 		if (!collectionTreeRow.editable) {
-			var wm = Components.classes["@mozilla.org/appshell/window-mediator;1"]
-					   .getService(Components.interfaces.nsIWindowMediator);
-			var win = wm.getMostRecentWindow("navigator:browser");
+			let win = Services.wm.getMostRecentWindow("navigator:browser");
 			win.ZoteroPane.displayCannotEditLibraryMessage();
 			return;
 		}
@@ -3256,9 +3254,7 @@ Zotero.ItemTreeView.prototype.drop = Zotero.Promise.coroutine(function* (row, or
 				if (dataType == 'text/x-moz-url') {
 					var url = data[i];
 					if (url.indexOf('file:///') == 0) {
-						var wm = Components.classes["@mozilla.org/appshell/window-mediator;1"]
-								   .getService(Components.interfaces.nsIWindowMediator);
-						var win = wm.getMostRecentWindow("navigator:browser");
+						let win = Services.wm.getMostRecentWindow("navigator:browser");
 						// If dragging currently loaded page, only convert to
 						// file if not an HTML document
 						if (win.content.location.href != url ||
@@ -3278,9 +3274,7 @@ Zotero.ItemTreeView.prototype.drop = Zotero.Promise.coroutine(function* (row, or
 					if (typeof file == 'string') {
 						if (parentItemID) {
 							if (!collectionTreeRow.filesEditable) {
-								var wm = Components.classes["@mozilla.org/appshell/window-mediator;1"]
-										   .getService(Components.interfaces.nsIWindowMediator);
-								var win = wm.getMostRecentWindow("navigator:browser");
+								let win = Services.wm.getMostRecentWindow("navigator:browser");
 								win.ZoteroPane.displayCannotEditLibraryFilesMessage();
 								return;
 							}
@@ -3295,9 +3289,7 @@ Zotero.ItemTreeView.prototype.drop = Zotero.Promise.coroutine(function* (row, or
 							});
 						}
 						else {
-							var wm = Components.classes["@mozilla.org/appshell/window-mediator;1"]
-									   .getService(Components.interfaces.nsIWindowMediator);
-							var win = wm.getMostRecentWindow("navigator:browser");
+							let win = Services.wm.getMostRecentWindow("navigator:browser");
 							win.ZoteroPane.addItemFromURL(url, 'temporaryPDFHack'); // TODO: don't do this
 						}
 						continue;
@@ -3318,9 +3310,7 @@ Zotero.ItemTreeView.prototype.drop = Zotero.Promise.coroutine(function* (row, or
 				}
 				else {
 					if (file.leafName.endsWith(".lnk")) {
-						let wm = Components.classes["@mozilla.org/appshell/window-mediator;1"]
-						   .getService(Components.interfaces.nsIWindowMediator);
-						let win = wm.getMostRecentWindow("navigator:browser");
+						let win = Services.wm.getMostRecentWindow("navigator:browser");
 						win.ZoteroPane.displayCannotAddShortcutMessage(file.path);
 						continue;
 					}
diff --git a/chrome/content/zotero/zoteroPane.js b/chrome/content/zotero/zoteroPane.js
index f230f2aa3..6191b97ff 100644
--- a/chrome/content/zotero/zoteroPane.js
+++ b/chrome/content/zotero/zoteroPane.js
@@ -3310,9 +3310,7 @@ var ZoteroPane = new function()
 			else if (openInNewTab || !window.loadURI || uris.length > 1) {
 				// if no gBrowser, find it
 				if(!gBrowser) {
-					var wm = Components.classes["@mozilla.org/appshell/window-mediator;1"]
-									   .getService(Components.interfaces.nsIWindowMediator);
-					var browserWindow = wm.getMostRecentWindow("navigator:browser");
+					let browserWindow = Services.wm.getMostRecentWindow("navigator:browser");
 					var gBrowser = browserWindow.gBrowser;
 				}