diff --git a/phpBB/phpbb/mention/source/base_group.php b/phpBB/phpbb/mention/source/base_group.php
index c8d498ce81..1f3f063e33 100644
--- a/phpBB/phpbb/mention/source/base_group.php
+++ b/phpBB/phpbb/mention/source/base_group.php
@@ -36,6 +36,9 @@ abstract class base_group implements source_interface
 	/** @var string */
 	protected $php_ext;
 
+	/** @var string|false */
+	protected $cache_ttl = false;
+
 	/** @var array Fetched groups' data */
 	protected $groups = null;
 
@@ -125,8 +128,8 @@ abstract class base_group implements source_interface
 	 */
 	public function get(array &$names, $keyword, $topic_id)
 	{
-		// Grab all group IDs, cache for 5 minutes
-		$result = $this->db->sql_query($this->query($keyword, $topic_id), 300);
+		// Grab all group IDs and cache them if needed
+		$result = $this->db->sql_query($this->query($keyword, $topic_id), $this->cache_ttl);
 
 		$group_ids = [];
 		while ($row = $this->db->sql_fetchrow($result))
diff --git a/phpBB/phpbb/mention/source/base_user.php b/phpBB/phpbb/mention/source/base_user.php
index e002840614..8b6c7a8540 100644
--- a/phpBB/phpbb/mention/source/base_user.php
+++ b/phpBB/phpbb/mention/source/base_user.php
@@ -30,6 +30,9 @@ abstract class base_user implements source_interface
 	/** @var string */
 	protected $php_ext;
 
+	/** @var string|false */
+	protected $cache_ttl = false;
+
 	/**
 	 * Constructor
 	 */
@@ -73,47 +76,67 @@ abstract class base_user implements source_interface
 		$fetched_all = false;
 		$keyword = utf8_clean_string($keyword);
 
-		// Grab all necessary user IDs, cache results for 5 minutes
-		$result = $this->db->sql_query($this->query($keyword, $topic_id), 300);
-
 		$i = 0;
 		$users = [];
 		$user_ids = [];
-		while ($i < $this->config['mention_batch_size'])
+
+		// Grab all necessary user IDs and cache them if needed
+		if ($this->cache_ttl)
 		{
-			$row = $this->db->sql_fetchrow($result);
+			$result = $this->db->sql_query($this->query($keyword, $topic_id), $this->cache_ttl);
 
-			if (!$row)
+			while ($i < $this->config['mention_batch_size'])
 			{
-				$fetched_all = true;
-				break;
-			}
+				$row = $this->db->sql_fetchrow($result);
 
-			if (!empty($keyword) && strpos($row['username_clean'], $keyword) !== 0)
-			{
-				continue;
-			}
+				if (!$row)
+				{
+					$fetched_all = true;
+					break;
+				}
 
-			$i++;
-			$users[] = $row;
-			$user_ids[] = $row['user_id'];
-		}
-
-		// Determine whether all usernames were fetched in current batch
-		if (!$fetched_all)
-		{
-			$fetched_all = true;
-
-			while ($row = $this->db->sql_fetchrow($result))
-			{
 				if (!empty($keyword) && strpos($row['username_clean'], $keyword) !== 0)
 				{
 					continue;
 				}
 
-				// At least one username hasn't been fetched - exit loop
-				$fetched_all = false;
-				break;
+				$i++;
+				$users[] = $row;
+				$user_ids[] = $row['user_id'];
+			}
+
+			// Determine whether all usernames were fetched in current batch
+			if (!$fetched_all)
+			{
+				$fetched_all = true;
+
+				while ($row = $this->db->sql_fetchrow($result))
+				{
+					if (!empty($keyword) && strpos($row['username_clean'], $keyword) !== 0)
+					{
+						continue;
+					}
+
+					// At least one username hasn't been fetched - exit loop
+					$fetched_all = false;
+					break;
+				}
+			}
+		}
+		else
+		{
+			$result = $this->db->sql_query_limit($this->query($keyword, $topic_id), $this->config['mention_batch_size'], 0);
+
+			while ($row = $this->db->sql_fetchrow($result))
+			{
+				$users[] = $row;
+				$user_ids[] = $row['user_id'];
+			}
+
+			// Determine whether all usernames were fetched in current batch
+			if (count($user_ids) < $this->config['mention_batch_size'])
+			{
+				$fetched_all = true;
 			}
 		}
 
diff --git a/phpBB/phpbb/mention/source/friend.php b/phpBB/phpbb/mention/source/friend.php
index f68bea175a..ca16a374b5 100644
--- a/phpBB/phpbb/mention/source/friend.php
+++ b/phpBB/phpbb/mention/source/friend.php
@@ -50,7 +50,8 @@ class friend extends base_user
 				]
 			],
 			'WHERE'     => 'z.friend = 1 AND z.user_id = ' . (int) $this->user->data['user_id'] . '
-				AND ' . $this->db->sql_in_set('u.user_type', [USER_NORMAL, USER_FOUNDER]),
+				AND ' . $this->db->sql_in_set('u.user_type', [USER_NORMAL, USER_FOUNDER]) . '
+				AND u.username_clean ' . $this->db->sql_like_expression($keyword . $this->db->get_any_char()),
 			'ORDER_BY'  => 'u.user_lastvisit DESC'
 		]);
 		return $query;
diff --git a/phpBB/phpbb/mention/source/group.php b/phpBB/phpbb/mention/source/group.php
index e74948d402..2b13ca7be0 100644
--- a/phpBB/phpbb/mention/source/group.php
+++ b/phpBB/phpbb/mention/source/group.php
@@ -15,6 +15,9 @@ namespace phpbb\mention\source;
 
 class group extends base_group
 {
+	/** @var string|false */
+	protected $cache_ttl = 300;
+
 	/**
 	 * {@inheritdoc}
 	 */
diff --git a/phpBB/phpbb/mention/source/team.php b/phpBB/phpbb/mention/source/team.php
index 4b40d7f224..14281a85bf 100644
--- a/phpBB/phpbb/mention/source/team.php
+++ b/phpBB/phpbb/mention/source/team.php
@@ -15,6 +15,9 @@ namespace phpbb\mention\source;
 
 class team extends base_user
 {
+	/** @var string|false */
+	protected $cache_ttl = 300;
+
 	/**
 	 * {@inheritdoc}
 	 */
diff --git a/phpBB/phpbb/mention/source/topic.php b/phpBB/phpbb/mention/source/topic.php
index 51b855e97b..0c630aa22e 100644
--- a/phpBB/phpbb/mention/source/topic.php
+++ b/phpBB/phpbb/mention/source/topic.php
@@ -61,7 +61,8 @@ class topic extends base_user
 				],
 			],
 			'WHERE'     => 'p.topic_id = ' . (int) $topic_id . '
-				AND ' . $this->db->sql_in_set('u.user_type', [USER_NORMAL, USER_FOUNDER]),
+				AND ' . $this->db->sql_in_set('u.user_type', [USER_NORMAL, USER_FOUNDER]) . '
+				AND u.username_clean ' . $this->db->sql_like_expression($keyword . $this->db->get_any_char()),
 			'ORDER_BY'  => 'p.post_time DESC'
 		]);
 		return $query;
diff --git a/phpBB/phpbb/mention/source/user.php b/phpBB/phpbb/mention/source/user.php
index 57f1a23eab..a85d3d3be4 100644
--- a/phpBB/phpbb/mention/source/user.php
+++ b/phpBB/phpbb/mention/source/user.php
@@ -39,7 +39,8 @@ class user extends base_user
 			'FROM'      => [
 				USERS_TABLE => 'u',
 			],
-			'WHERE'     => $this->db->sql_in_set('u.user_type', [USER_NORMAL, USER_FOUNDER]),
+			'WHERE'     => $this->db->sql_in_set('u.user_type', [USER_NORMAL, USER_FOUNDER]) . '
+				AND u.username_clean ' . $this->db->sql_like_expression($keyword . $this->db->get_any_char()),
 			'ORDER_BY'  => 'u.user_lastvisit DESC'
 		]);
 		return $query;