diff --git a/phpBB/install/schemas/schema.json b/phpBB/install/schemas/schema.json
index a3ffd923a1..1a9b9b62b7 100644
--- a/phpBB/install/schemas/schema.json
+++ b/phpBB/install/schemas/schema.json
@@ -2397,14 +2397,6 @@
             ]
         },
         "KEYS": {
-            "unq_mtch": [
-                "UNIQUE",
-                [
-                    "word_id",
-                    "post_id",
-                    "title_match"
-                ]
-            ],
             "word_id": [
                 "INDEX",
                 "word_id"
@@ -2412,6 +2404,14 @@
             "post_id": [
                 "INDEX",
                 "post_id"
+            ],
+            "un_mtch": [
+                "UNIQUE",
+                [
+                    "word_id",
+                    "post_id",
+                    "title_match"
+                ]
             ]
         }
     },
diff --git a/phpBB/phpbb/db/migration/data/v310/rename_too_long_indexes.php b/phpBB/phpbb/db/migration/data/v310/rename_too_long_indexes.php
new file mode 100644
index 0000000000..8d2a15d8ea
--- /dev/null
+++ b/phpBB/phpbb/db/migration/data/v310/rename_too_long_indexes.php
@@ -0,0 +1,38 @@
+<?php
+/**
+*
+* This file is part of the phpBB Forum Software package.
+*
+* @copyright (c) phpBB Limited <https://www.phpbb.com>
+* @license GNU General Public License, version 2 (GPL-2.0)
+*
+* For full copyright and license information, please see
+* the docs/CREDITS.txt file.
+*
+*/
+
+namespace phpbb\db\migration\data\v310;
+
+class rename_too_long_indexes extends \phpbb\db\migration\migration
+{
+	static public function depends_on()
+	{
+		return array('\phpbb\db\migration\data\v30x\release_3_0_0');
+	}
+
+	public function update_schema()
+	{
+		return array(
+			'drop_keys' => array(
+				$this->table_prefix . 'search_wordmatch' => array(
+					'unq_mtch',
+				),
+			),
+			'add_unique_index' => array(
+				$this->table_prefix . 'search_wordmatch' => array(
+					'un_mtch'	=> array('word_id', 'post_id', 'title_match'),
+				),
+			),
+		);
+	}
+}
diff --git a/phpBB/phpbb/db/tools.php b/phpBB/phpbb/db/tools.php
index ae0c695aa2..5d93eb8246 100644
--- a/phpBB/phpbb/db/tools.php
+++ b/phpBB/phpbb/db/tools.php
@@ -2104,7 +2104,7 @@ class tools
 		$statements = array();
 
 		$table_prefix = substr(CONFIG_TABLE, 0, -6); // strlen(config)
-		if (strlen($table_name . $index_name) - strlen($table_prefix) > 24)
+		if (strlen($table_name . '_' . $index_name) - strlen($table_prefix) > 24)
 		{
 			$max_length = strlen($table_prefix) + 24;
 			trigger_error("Index name '{$table_name}_$index_name' on table '$table_name' is too long. The maximum is $max_length characters.", E_USER_ERROR);