diff --git a/chrome/content/zotero/xpcom/http.js b/chrome/content/zotero/xpcom/http.js
index a82b31690..71f41814e 100644
--- a/chrome/content/zotero/xpcom/http.js
+++ b/chrome/content/zotero/xpcom/http.js
@@ -525,8 +525,7 @@ Zotero.HTTP = new function() {
 	
 	
 	/**
-	 * Make a foreground HTTP request in order to trigger a proxy authentication
-	 * dialog in Standalone
+	 * Make a foreground HTTP request in order to trigger a proxy authentication dialog
 	 *
 	 * Other Zotero.HTTP requests are background requests by default, and
 	 * background requests don't trigger a proxy auth prompt, so we make a
@@ -551,8 +550,7 @@ Zotero.HTTP = new function() {
 			uris.unshift(ZOTERO_CONFIG.PROXY_AUTH_URL);
 			
 			return Zotero.spawn(function* () {
-				let max = 3; // how many URIs to try after the general Zotero one
-				for (let i = 0; i <= max; i++) {
+				for (let i = 0; i <= uris.length; i++) {
 					let uri = uris.shift();
 					if (!uri) {
 						break;
@@ -589,7 +587,7 @@ Zotero.HTTP = new function() {
 					let proxyInfo = yield _proxyAsyncResolve(uri);
 					if (proxyInfo) {
 						Zotero.debug("Proxy required for " + uri + " -- making HEAD request to trigger auth prompt");
-						yield Zotero.HTTP.promise("HEAD", uri, {
+						yield Zotero.HTTP.request("HEAD", uri, {
 							foreground: true,
 							dontCache: true
 						})
diff --git a/defaults/preferences/zotero.js b/defaults/preferences/zotero.js
index 6fcc0fd8d..642ed2d93 100644
--- a/defaults/preferences/zotero.js
+++ b/defaults/preferences/zotero.js
@@ -23,7 +23,7 @@ pref("extensions.zotero.automaticScraperUpdates",true);
 pref("extensions.zotero.zoteroDotOrgVersionHeader", true);
 pref("extensions.zotero.triggerProxyAuthentication", true);
 // Proxy auth URLs should respond successfully to HEAD requests over HTTP and HTTPS (in case of forced HTTPS requests)
-pref("extensions.zotero.proxyAuthenticationURLs", 'http://www.acm.org,http://www.ebscohost.com,http://www.elsevier.com,http://www.ieee.org,http://www.jstor.org,http://www.ovid.com,http://www.springer.com,http://www.tandfonline.com');
+pref("extensions.zotero.proxyAuthenticationURLs", 'https://www.acm.org,https://www.ebscohost.com,https://www.sciencedirect.com,https://ieeexplore.ieee.org,https://www.jstor.org,http://www.ovid.com,https://link.springer.com,https://www.tandfonline.com');
 pref("extensions.zotero.browserContentContextMenu", true);
 pref("extensions.zotero.openURL.resolver","http://worldcatlibraries.org/registry/gateway");
 pref("extensions.zotero.openURL.version","1.0");