diff --git a/phpBB/includes/acp/acp_styles.php b/phpBB/includes/acp/acp_styles.php
index a57c509abe..fc6cf26f70 100644
--- a/phpBB/includes/acp/acp_styles.php
+++ b/phpBB/includes/acp/acp_styles.php
@@ -398,7 +398,9 @@ class acp_styles
 
 		// Reset default style for users who use selected styles
 		$sql = 'UPDATE ' . USERS_TABLE . '
-			SET user_style = ' . $this->default_style . '
+			SET user_style = ' . (int) $this->default_style 
+. 
+'
 			WHERE user_style IN (' . implode(', ', $ids) . ')';
 		$this->db->sql_query($sql);
 
@@ -1249,7 +1251,9 @@ class acp_styles
 
 		// Change default style for users
 		$sql = 'UPDATE ' . USERS_TABLE . '
-			SET user_style = ' . $this->default_style . '
+			SET user_style = ' . (int) $this->default_style 
+. 
+'
 			WHERE user_style = ' . $id;
 		$this->db->sql_query($sql);