diff --git a/chrome/content/zotero/xpcom/proxy.js b/chrome/content/zotero/xpcom/proxy.js
index 2cafe366bd..074090251e 100644
--- a/chrome/content/zotero/xpcom/proxy.js
+++ b/chrome/content/zotero/xpcom/proxy.js
@@ -23,6 +23,8 @@
     ***** END LICENSE BLOCK *****
 */
 
+Components.utils.importGlobalProperties(["URL"]);
+
 /**
  * A singleton to handle URL rewriting proxies
  * @namespace
@@ -139,12 +141,7 @@ Zotero.Proxies = new function() {
 	 */
 	this.proxyToProper = function(url, onlyReturnIfProxied) {
 		// make sure url has a trailing slash
-		if (typeof URL === 'undefined') {
-			url = new (Services.wm.getMostRecentWindow("navigator:browser")).URL(url).href;
-		}
-		else {
-			url = new URL(url).href;
-		}
+		url = new URL(url).href;
 		for (let proxy of Zotero.Proxies.proxies) {
 			if(proxy.regexp) {
 				var m = proxy.regexp.exec(url);
@@ -185,12 +182,7 @@ Zotero.Proxies = new function() {
 	 */
 	this.getPotentialProxies = function(url) {
 		// make sure url has a trailing slash
-		if (typeof URL === 'undefined') {
-			url = new (Services.wm.getMostRecentWindow("navigator:browser")).URL(url).href;
-		}
-		else {
-			url = new URL(url).href;
-		}
+		url = new URL(url).href;
 		var urlToProxy = {};
 		// If it's a known proxied URL just return it
 		if (Zotero.Proxies.transparent) {
diff --git a/test/tests/proxyTest.js b/test/tests/proxyTest.js
index 6cfc4d75a9..af07821487 100644
--- a/test/tests/proxyTest.js
+++ b/test/tests/proxyTest.js
@@ -11,20 +11,20 @@ describe("Zotero.Proxies", function(){
 		});
 		
 		it("should return the provided url and deproxied url", function() {
-			let url = "https://www.example.com.proxy.example.com";
+			let url = "https://www.example.com.proxy.example.com/";
 			let proxies = Zotero.Proxies.getPotentialProxies(url);
 			let expectedProxies = {};
 			expectedProxies[url] = null;
-			expectedProxies["https://www.example.com"] = {scheme: "https://%h.proxy.example.com/%p"};
+			expectedProxies["https://www.example.com/"] = {scheme: "https://%h.proxy.example.com/%p"};
 			assert.deepEqual(proxies, expectedProxies);
 		});
 		
 		it("should return the provided url and deproxied url with replaced hyphens", function() {
-			let url = "https://www-example-com.proxy.example.com";
+			let url = "https://www-example-com.proxy.example.com/";
 			let proxies = Zotero.Proxies.getPotentialProxies(url);
 			let expectedProxies = {};
 			expectedProxies[url] = null;
-			expectedProxies["https://www.example.com"] = {scheme: "https://%h.proxy.example.com/%p"};
+			expectedProxies["https://www.example.com/"] = {scheme: "https://%h.proxy.example.com/%p"};
 			assert.deepEqual(proxies, expectedProxies);
 		});
 	});