diff --git a/api/js/jsapi/egw_json.js b/api/js/jsapi/egw_json.js
index 7e402bd921..dad1ebc5ef 100644
--- a/api/js/jsapi/egw_json.js
+++ b/api/js/jsapi/egw_json.js
@@ -285,7 +285,7 @@ egw.extend('json', egw.MODULE_WND_LOCAL, function(_app, _wnd)
 				})
 			}
 			const date = typeof response.headers === 'object' ? 'Date: '+response.headers.get('Date') :
-				response.getAllResponseHeaders().match(/^Date:.*$/mi)[0] ||
+				(typeof response.getAllResponseHeaders === 'function' ? response.getAllResponseHeaders().match(/^Date:.*$/mi)[0] : null) ||
 				'Date: '+(new Date).toString();
 			this.egw.message.call(this.egw,
 				this.egw.lang('A request to the EGroupware server returned with an error')+
@@ -416,7 +416,7 @@ egw.extend('json', egw.MODULE_WND_LOCAL, function(_app, _wnd)
 				}
 			}
 			// Call request callback, if provided
-			if(this.callback != null && !only_data)
+			if(typeof this.callback === 'function' && !only_data)
 			{
 				this.callback.call(this.context,res);
 			}
diff --git a/api/js/jsapi/egw_preferences.js b/api/js/jsapi/egw_preferences.js
index a57cdf54f7..bd3d9d3e22 100644
--- a/api/js/jsapi/egw_preferences.js
+++ b/api/js/jsapi/egw_preferences.js
@@ -53,31 +53,47 @@ egw.extend('preferences', egw.MODULE_GLOBAL, function()
 		/**
 		 * Query an EGroupware user preference
 		 *
-		 * If a prefernce is not already loaded (only done for "common" by default), it is synchroniosly queryed from the server!
+		 * If a preference is not already loaded (only done for "common" by default),
+		 * it is synchronously queried from the server, if no _callback parameter is given!
 		 *
 		 * @param {string} _name name of the preference, eg. 'dateformat', or '*' to get all the application's preferences
 		 * @param {string} _app default 'common'
-		 * @param {function|false|undefined} _callback optional callback, if preference needs loading first
-		 * if false given and preference is not loaded, undefined is return and no (synchronious) request is send to server
+		 * @param {function|boolean|undefined} _callback optional callback, if preference needs loading first
+		 *  - default/undefined: preference is synchronously queried, if not loaded, and returned
+		 *  - function: if loaded, preference is returned, if not false and callback is called once it's loaded
+		 * 	- true:  a promise for the preference is returned
+		 *	- false: if preference is not loaded, undefined is return and no (synchronous) request is send to server
 		 * @param {object} _context context for callback
-		 * @return string|bool preference value or false, if callback given and preference not yet loaded
+		 * @return Promise|object|string|bool (Promise for) preference value or false, if callback given and preference not yet loaded
 		 */
 		preference: function(_name, _app, _callback, _context)
 		{
-			if (typeof _app == 'undefined') _app = 'common';
+			if (typeof _app === 'undefined') _app = 'common';
 
-			if (typeof prefs[_app] == 'undefined')
+			if (typeof prefs[_app] === 'undefined')
 			{
 				if (_callback === false) return undefined;
-				var request = this.json('EGroupware\\Api\\Framework::ajax_get_preference', [_app], _callback, _context);
-				request.sendRequest(typeof _callback == 'function', 'GET');	// use synchronous (cachable) GET request
-				if (typeof prefs[_app] == 'undefined') prefs[_app] = {};
-				if (typeof _callback == 'function') return false;
+				const request = this.json('EGroupware\\Api\\Framework::ajax_get_preference', [_app], _callback, _context);
+				const promise = request.sendRequest(typeof _callback !== 'undefined', 'GET');
+				if (typeof prefs[_app] === 'undefined') prefs[_app] = {};
+				if (_callback === true) return promise.then(() => this.preference(_name, _app));
+				if (typeof _callback === 'function') return false;
 			}
-			if (_name == "*") return typeof prefs[_app] ==='object' ? jQuery.extend({},prefs[_app]) : prefs[_app];
-
-			return typeof prefs[_app][_name] === 'object' && prefs[_app][_name] !== null ?
-				jQuery.extend({},prefs[_app][_name]) : prefs[_app][_name];
+			let ret;
+			if (_name === "*")
+			{
+				ret = typeof prefs[_app] === 'object' ? jQuery.extend({}, prefs[_app]) : prefs[_app];
+			}
+			else
+			{
+				ret = typeof prefs[_app][_name] === 'object' && prefs[_app][_name] !== null ?
+					jQuery.extend({}, prefs[_app][_name]) : prefs[_app][_name];
+			}
+			if (_callback === true)
+			{
+				return Promise.resolve(ret);
+			}
+			return ret;
 		},
 
 		/**
diff --git a/notifications/js/notificationajaxpopup.js b/notifications/js/notificationajaxpopup.js
index 48b29712b1..b2dc13bfae 100644
--- a/notifications/js/notificationajaxpopup.js
+++ b/notifications/js/notificationajaxpopup.js
@@ -908,7 +908,10 @@
 
 		var self = notifications;
 		var langRequire = jQuery('#notifications_script_id').attr('data-langRequire');
-		egw.langRequire(window, [JSON.parse(langRequire)]).then(()=>
+		Promise.all([
+			egw.langRequire(window, [JSON.parse(langRequire)]),
+			egw.preference('notification_chain','notifications', true)
+		]).then(() =>
 		{
 			var $egwpopup_fw = jQuery('#topmenu_info_notifications');
 			switch (egw.preference('notification_chain','notifications'))