diff --git a/phpBB/assets/javascript/editor.js b/phpBB/assets/javascript/editor.js
index 9972ffdd6a..b6382304bc 100644
--- a/phpBB/assets/javascript/editor.js
+++ b/phpBB/assets/javascript/editor.js
@@ -387,15 +387,35 @@ function getCaretPosition(txtarea) {
 (function($) {
 	function Mentions() {
 		let $mentionDataContainer = $('[data-mention-url]:first');
+		let mentionURL = $mentionDataContainer.data('mentionUrl');
+		let mentionBatchSize = $mentionDataContainer.data('mentionBatchSize');
+		let mentionNamesLimit = $mentionDataContainer.data('mentionNamesLimit');
+		let mentionTopicId = $mentionDataContainer.data('topicId');
 		let queryInProgress = null;
-		let cachedNames = null;
-		let cachedFor = null;
+		let cachedNames = [];
 		let cachedSearchKey = 'name';
 
 		function defaultAvatar(type) {
 			return (type === 'group') ? '<svg class="mention-media-avatar" xmlns="http://www.w3.org/2000/svg" viewbox="0 0 24 24"><path fill-rule="evenodd" d="M16 11c1.66 0 2.99-1.34 2.99-3S17.66 5 16 5c-1.66 0-3 1.34-3 3s1.34 3 3 3zm-8 0c1.66 0 2.99-1.34 2.99-3S9.66 5 8 5C6.34 5 5 6.34 5 8s1.34 3 3 3zm0 2c-2.33 0-7 1.17-7 3.5V19h14v-2.5c0-2.33-4.67-3.5-7-3.5zm8 0c-.29 0-.62.02-.97.05 1.16.84 1.97 1.97 1.97 3.45V19h6v-2.5c0-2.33-4.67-3.5-7-3.5z"/></svg>' : '<svg class="mention-media-avatar" xmlns="http://www.w3.org/2000/svg" viewbox="0 0 24 24"><path fill-rule="evenodd" d="M12,19.2C9.5,19.2 7.29,17.92 6,16C6.03,14 10,12.9 12,12.9C14,12.9 17.97,14 18,16C16.71,17.92 14.5,19.2 12,19.2M12,5A3,3 0 0,1 15,8A3,3 0 0,1 12,11A3,3 0 0,1 9,8A3,3 0 0,1 12,5M12,2A10,10 0 0,0 2,12A10,10 0 0,0 12,22A10,10 0 0,0 22,12C22,6.47 17.5,2 12,2Z"/></svg>';
 		}
 
+		function getCachedNames(query) {
+			if (!cachedNames) {
+				return null;
+			}
+
+			let i;
+
+			for (i = query.length; i > 0; i--) {
+				let startStr = query.substr(0, i);
+				if (cachedNames[startStr]) {
+					return cachedNames[startStr];
+				}
+			}
+
+			return cachedNames[''];
+		}
+
 		function getMatchedNames(query, items, searchKey) {
 			let i;
 			let len;
@@ -413,15 +433,50 @@ function getCaretPosition(txtarea) {
 			return getMatchedNames(query, cachedNames, cachedSearchKey).length;
 		}
 
+		function remoteFilter(query, callback) {
+			/*
+			* Do not make a new request until the previous one for the same query is returned
+			* This fixes duplicate server queries e.g. when arrow keys are pressed
+			*/
+			if (queryInProgress === query) {
+				setTimeout(function() {
+					remoteFilter(query, callback);
+				}, 1000);
+				return;
+			}
+
+			let cachedNamesForQuery = getCachedNames(query);
+
+			/*
+			* Use cached values when we can:
+			* 1) There are some names in the cache relevant for the query
+			*    (cache for the query with the same first characters cointains some data)
+			* 2) We have enough names to display OR
+			*    all relevant names have been fetched from the server
+			*/
+			if (cachedNamesForQuery &&
+				(getNumberOfMatchedCachedNames(query) >= mentionNamesLimit ||
+					cachedNamesForQuery.length < mentionBatchSize)) {
+				callback(cachedNamesForQuery);
+				return;
+			}
+
+			queryInProgress = query;
+
+			let params = {keyword: query, topic_id: mentionTopicId, _referer: location.href};
+			$.getJSON(mentionURL, params, function(data) {
+				cachedNames[query] = data;
+				callback(data);
+			}).always(function() {
+				queryInProgress = null;
+			});
+		}
+
 		this.isEnabled = function() {
 			return $mentionDataContainer.length;
 		};
 
 		this.handle = function(txtarea) {
-			let mentionURL = $mentionDataContainer.data('mentionUrl');
-			let mentionBatchSize = $mentionDataContainer.data('mentionBatchSize');
-			let mentionNamesLimit = $mentionDataContainer.data('mentionNamesLimit');
-			let mentionTopicId = $mentionDataContainer.data('topicId');
 			$(txtarea).atwho({
 				at: "@",
 				acceptSpaceBar: true,
@@ -434,40 +489,7 @@ function getCaretPosition(txtarea) {
 				insertTpl: "[mention=${type}:${id}]${name}[/mention]",
 				limit: mentionNamesLimit,
 				callbacks: {
-					remoteFilter: function(query, callback) {
-						/*
-						* Use cached values when we can:
-						* 1) There are some names in the cache
-						* 2) The cache contains relevant data for the query
-						*    (it was made for the query with the same first characters)
-						* 3) We have enough names to display OR
-						*    all relevant names have been fetched from the server
-						*/
-						if (cachedNames &&
-							query.indexOf(cachedFor) === 0 &&
-							(getNumberOfMatchedCachedNames(query) >= mentionNamesLimit ||
-								cachedNames.length < mentionBatchSize)) {
-							callback(cachedNames);
-							return;
-						}
-
-						/*
-						* Do not make a new request until the previous one for the same query is returned
-						* This fixes duplicate server queries e.g. when arrow keys are pressed
-						*/
-						if (queryInProgress === query) {
-							return;
-						}
-						queryInProgress = query;
-
-						let params = {keyword: query, topic_id: mentionTopicId, _referer: location.href};
-						$.getJSON(mentionURL, params, function (data) {
-							cachedNames = data;
-							cachedFor = query;
-							queryInProgress = null;
-							callback(data);
-						});
-					},
+					remoteFilter: remoteFilter,
 					sorter: function(query, items, searchKey) {
 						let i;
 						let len;