diff --git a/phpBB/includes/acp/acp_attachments.php b/phpBB/includes/acp/acp_attachments.php
index b0e086e65c..8cb5f5f970 100644
--- a/phpBB/includes/acp/acp_attachments.php
+++ b/phpBB/includes/acp/acp_attachments.php
@@ -1079,7 +1079,7 @@ class acp_attachments
 				$attachments_per_page = (int) $config['topics_per_page'];
 
 				// Get total number or orphans older than 3 hours
-				$sql = 'SELECT COUNT(attach_id) as num_files, SUM(filesize) as total_size
+				$sql = 'SELECT COUNT(attach_id) as num_files, SUM(' . $this->db->cast_expr_to_bigint('filesize') . ') as total_size
 					FROM ' . ATTACHMENTS_TABLE . '
 					WHERE is_orphan = 1
 						AND filetime < ' . (time() - 3*60*60);
diff --git a/phpBB/includes/acp/acp_forums.php b/phpBB/includes/acp/acp_forums.php
index 920214448d..abd622fe9d 100644
--- a/phpBB/includes/acp/acp_forums.php
+++ b/phpBB/includes/acp/acp_forums.php
@@ -2048,7 +2048,7 @@ class acp_forums
 
 		$config->set('num_files', (int) $row['stat'], false);
 
-		$sql = 'SELECT SUM(filesize) as stat
+		$sql = 'SELECT SUM(' . $db->cast_expr_to_bigint('filesize') . ') as stat
 			FROM ' . ATTACHMENTS_TABLE;
 		$result = $db->sql_query($sql);
 		$row = $db->sql_fetchrow($result);
diff --git a/phpBB/includes/acp/acp_main.php b/phpBB/includes/acp/acp_main.php
index b29e3f7ad1..83df4dc073 100644
--- a/phpBB/includes/acp/acp_main.php
+++ b/phpBB/includes/acp/acp_main.php
@@ -189,7 +189,7 @@ class acp_main
 						$config->set('num_files', (int) $db->sql_fetchfield('stat'), false);
 						$db->sql_freeresult($result);
 
-						$sql = 'SELECT SUM(filesize) as stat
+						$sql = 'SELECT SUM(' . $db->cast_expr_to_bigint('filesize') . ') as stat
 							FROM ' . ATTACHMENTS_TABLE . '
 							WHERE is_orphan = 0';
 						$result = $db->sql_query($sql);
diff --git a/phpBB/includes/functions_convert.php b/phpBB/includes/functions_convert.php
index cf2a659d77..8a161edfa7 100644
--- a/phpBB/includes/functions_convert.php
+++ b/phpBB/includes/functions_convert.php
@@ -1845,7 +1845,7 @@ function update_dynamic_config()
 	$config->set('num_files', (int) $db->sql_fetchfield('stat'), false);
 	$db->sql_freeresult($result);
 
-	$sql = 'SELECT SUM(filesize) as stat
+	$sql = 'SELECT SUM(' . $db->cast_expr_to_bigint('filesize') . ') as stat
 		FROM ' . ATTACHMENTS_TABLE . '
 		WHERE is_orphan = 0';
 	$result = $db->sql_query($sql);