diff --git a/src/messenger/webim/install/dbinfo.php b/src/messenger/webim/install/dbinfo.php
index 919effb9..f512a585 100644
--- a/src/messenger/webim/install/dbinfo.php
+++ b/src/messenger/webim/install/dbinfo.php
@@ -129,6 +129,15 @@ $dbtables = array(
 	),
 );
 
+$dbtables_indexes = array(
+	"${mysqlprefix}chatmessage" => array(
+		"idx_agentid" => "agentid"
+	),
+	"${mysqlprefix}chatsitevisitor" => array(
+		"threadid" => "threadid"
+	)
+);
+
 $memtables = array();
 
 $dbtables_can_update = array(
@@ -157,7 +166,7 @@ function show_install_err($text)
 
 function create_table($id, $link)
 {
-	global $dbtables, $memtables, $dbencoding, $mysqlprefix;
+	global $dbtables, $dbtables_indexes, $memtables, $dbencoding, $mysqlprefix;
 
 	if (!isset($dbtables[$id])) {
 		show_install_err("Unknown table: $id, " . mysql_error($link));
@@ -170,6 +179,12 @@ function create_table($id, $link)
 		$query .= "	$k $v,\n";
 	}
 
+	if (isset($dbtables_indexes[$id])) {
+	    foreach ($dbtables_indexes[$id] as $k => $v) {
+		    $query .= "	INDEX $k ($v),\n";
+	    }
+	}
+
 	$query = preg_replace("/,\n$/", "", $query);
 	$query .= ") charset $dbencoding";
 	if (in_array($id, $memtables)) {