diff --git a/phpBB/docs/CHANGELOG.html b/phpBB/docs/CHANGELOG.html
index dd4ffbb4d1..4248dd3761 100644
--- a/phpBB/docs/CHANGELOG.html
+++ b/phpBB/docs/CHANGELOG.html
@@ -94,6 +94,7 @@
 		<li>[Fix] Correctly sort database backup file list by date on database restore page. (Bug #57385)</li>
 		<li>[Fix] Take admin's time zone settings into account when listing database backup files. (Bug #57385)</li>
 		<li>[Fix] Honor minimum and maximum password length in generated passwords as much as we can. (Bug #13181)</li>
+		<li>[Fix] No longer return the character O in generated random strings and passwords. (Bug #57345)</li>
 	</ul>
 
 	<a name="v306"></a><h3>1.ii. Changes since 3.0.6</h3>
diff --git a/phpBB/includes/functions.php b/phpBB/includes/functions.php
index 823c71dbf0..23221c69ea 100644
--- a/phpBB/includes/functions.php
+++ b/phpBB/includes/functions.php
@@ -202,7 +202,7 @@ function set_config_count($config_name, $increment, $is_dynamic = false)
 function gen_rand_string($num_chars = 8)
 {
 	$rand_str = unique_id();
-	$rand_str = str_replace('0', 'Z', strtoupper(base_convert($rand_str, 16, 35)));
+	$rand_str = str_replace(array('0', 'O'), array('Z', 'Y'), strtoupper(base_convert($rand_str, 16, 34)));
 
 	return substr($rand_str, 0, $num_chars);
 }