diff --git a/phpBB/includes/functions_user.php b/phpBB/includes/functions_user.php
index d019b867fa..5789981429 100644
--- a/phpBB/includes/functions_user.php
+++ b/phpBB/includes/functions_user.php
@@ -1760,6 +1760,13 @@ function validate_username($username, $allowed_username = false)
 		return 'USERNAME_TAKEN';
 	}
 
+	// Check for out-of-bounds characters that are currently
+	// not supported by utf8_bin in MySQL
+	if (preg_match('/[\x{10000}-\x{10FFFF}]/u', $username))
+	{
+		return 'INVALID_EMOJIS_USERNAME';
+	}
+
 	$sql = 'SELECT group_name
 		FROM ' . GROUPS_TABLE . "
 		WHERE LOWER(group_name) = '" . $db->sql_escape(utf8_strtolower($username)) . "'";
diff --git a/phpBB/language/en/ucp.php b/phpBB/language/en/ucp.php
index 5875099fb8..a4e834cb85 100644
--- a/phpBB/language/en/ucp.php
+++ b/phpBB/language/en/ucp.php
@@ -272,6 +272,7 @@ $lang = array_merge($lang, array(
 	'IMPORTANT_NEWS'			=> 'Important announcements',
 	'INVALID_USER_BIRTHDAY'			=> 'The entered birthday is not a valid date.',
 	'INVALID_CHARS_USERNAME'	=> 'The username contains forbidden characters.',
+	'INVALID_EMOJIS_USERNAME'	=> 'The username contains forbidden characters (Emoji).',
 	'INVALID_CHARS_NEW_PASSWORD'=> 'The password does not contain the required characters.',
 	'ITEMS_REQUIRED'			=> 'The items marked with * are required profile fields and need to be filled out.',