diff --git a/phpBB/docs/CHANGELOG.html b/phpBB/docs/CHANGELOG.html
index fd2d1496dc..62f4eeb1f8 100644
--- a/phpBB/docs/CHANGELOG.html
+++ b/phpBB/docs/CHANGELOG.html
@@ -100,6 +100,7 @@
 		<li>[Fix] Correctly apply the can change vote permission again. Regression introduced in r9470. (Bug #45895)</li>
 		<li>[Fix] Also remove data from friend/foe table when deleting user. (Bug #45345 - Patch by nickvergessen)</li>
 		<li>[Fix] Correctly hide skiplink in prosilver right-to-left mode. (Bug #45765 - Patch by prototech and bantu)</li>
+		<li>[Fix] Fix dynamic config update routine error if firebird is used (Bug #46315)</li>
 		<li>[Change] Change the data format of the default file ACM to be more secure from tampering and have better performance.</li>
 		<li>[Change] Add index on log_time to the log table to prevent slowdown on boards with many log entries. (Bug #44665 - Patch by bantu)</li>
 		<li>[Change] Template engine now permits to a limited extent variable includes.</li>
diff --git a/phpBB/includes/functions.php b/phpBB/includes/functions.php
index f958a204b6..188c8ee5e3 100644
--- a/phpBB/includes/functions.php
+++ b/phpBB/includes/functions.php
@@ -174,7 +174,7 @@ function set_config_count($config_name, $increment, $is_dynamic = false)
 	switch ($db->sql_layer)
 	{
 		case 'firebird':
-			$sql_update = 'CAST(CAST(config_value as integer) + ' . (int) $increment . ' as CHAR)';
+			$sql_update = 'CAST(CAST(config_value as integer) + ' . (int) $increment . ' as VARCHAR(255))';
 		break;
 
 		case 'postgres':