diff --git a/phpBB/docs/CHANGELOG.html b/phpBB/docs/CHANGELOG.html
index de03665e09..c624d9d004 100644
--- a/phpBB/docs/CHANGELOG.html
+++ b/phpBB/docs/CHANGELOG.html
@@ -280,6 +280,7 @@ p a {
 		<li>[Fix] Let polls be edited correctly (Bug #12433)</li>
 		<li>[Fix] Overcome Oracle's inability to handle IN() clauses with over one thousand elements (Bug #12449)</li>
 		<li>[Fix] Simulate Firebird's affected rows mechanism for older versions of PHP</li>
+		<li>[Fix] Custom BBCodes properly handle lowercasing of parameterized tags (Bug #12377)</li>
 
 </ul>
 
diff --git a/phpBB/includes/acp/acp_bbcodes.php b/phpBB/includes/acp/acp_bbcodes.php
index 99d7831390..1c43daf642 100644
--- a/phpBB/includes/acp/acp_bbcodes.php
+++ b/phpBB/includes/acp/acp_bbcodes.php
@@ -118,7 +118,7 @@ class acp_bbcodes
 				// Make sure the user didn't pick a "bad" name for the BBCode tag.
 				$hard_coded = array('code', 'quote', 'quote=', 'attachment', 'attachment=', 'b', 'i', 'url', 'url=', 'img', 'size', 'size=', 'color', 'color=', 'u', 'list', 'list=', 'email', 'email=', 'flash', 'flash=');
 
-				if (($action == 'modify' && $data['bbcode_tag'] !== $row['bbcode_tag']) || ($action == 'create'))
+				if (($action == 'modify' && strtolower($data['bbcode_tag']) !== strtolower($row['bbcode_tag'])) || ($action == 'create'))
 				{
 					$sql = 'SELECT 1 as test
 						FROM ' . BBCODES_TABLE . "
@@ -383,6 +383,7 @@ class acp_bbcodes
 
 		// Lowercase tags
 		$bbcode_tag = preg_replace('/.*?\[([a-z0-9_-]+=?).*/i', '$1', $bbcode_match);
+		$bbcode_search = preg_replace('/.*?\[([a-z0-9_-]+)=?.*/i', '$1', $bbcode_match);
 
 		if (!preg_match('/^[a-zA-Z0-9_-]+=?$/', $bbcode_tag))
 		{
@@ -390,10 +391,10 @@ class acp_bbcodes
 			trigger_error($user->lang['BBCODE_INVALID'] . adm_back_link($this->u_action), E_USER_WARNING);
 		}
 
-		$fp_match = preg_replace('#\[/?' . $bbcode_tag . '#ie', "strtolower('\$0')", $fp_match);
-		$fp_replace = preg_replace('#\[/?' . $bbcode_tag . '#ie', "strtolower('\$0')", $fp_replace);
-		$sp_match = preg_replace('#\[/?' . $bbcode_tag . '#ie', "strtolower('\$0')", $sp_match);
-		$sp_replace = preg_replace('#\[/?' . $bbcode_tag . '#ie', "strtolower('\$0')", $sp_replace);
+		$fp_match = preg_replace('#\[/?' . $bbcode_search . '#ie', "strtolower('\$0')", $fp_match);
+		$fp_replace = preg_replace('#\[/?' . $bbcode_search . '#ie', "strtolower('\$0')", $fp_replace);
+		$sp_match = preg_replace('#\[/?' . $bbcode_search . '#ie', "strtolower('\$0')", $sp_match);
+		$sp_replace = preg_replace('#\[/?' . $bbcode_search . '#ie', "strtolower('\$0')", $sp_replace);
 
 		return array(
 			'bbcode_tag'				=> $bbcode_tag,