diff --git a/phpBB/includes/acp/acp_main.php b/phpBB/includes/acp/acp_main.php
index ffc830ec90..75c717728d 100644
--- a/phpBB/includes/acp/acp_main.php
+++ b/phpBB/includes/acp/acp_main.php
@@ -679,7 +679,11 @@ class acp_main
 			}
 		}
 
-		if (!defined('PHPBB_DISABLE_CONFIG_CHECK') && file_exists($phpbb_root_path . 'config.' . $phpEx) && $phpbb_filesystem->is_writable($phpbb_root_path . 'config.' . $phpEx))
+		$config_ref = $phpbb_root_path . 'config.' . $phpEx;
+
+		if (!defined('PHPBB_DISABLE_CONFIG_CHECK') && file_exists($phpbb_root_path . 'config.' . $phpEx)
+			&& (function_exists('is_writable') ? is_writable($config_ref) : $phpbb_filesystem->is_writable($config_ref))
+		)
 		{
 			// World-Writable? (000x)
 			$template->assign_var('S_WRITABLE_CONFIG', (bool) (@fileperms($phpbb_root_path . 'config.' . $phpEx) & 0x0002));
diff --git a/phpBB/phpbb/filesystem/filesystem.php b/phpBB/phpbb/filesystem/filesystem.php
index 3749d12b48..7f44d5f1de 100644
--- a/phpBB/phpbb/filesystem/filesystem.php
+++ b/phpBB/phpbb/filesystem/filesystem.php
@@ -613,8 +613,11 @@ class filesystem implements filesystem_interface
 			}
 			else
 			{
-				if (is_writable($file))
+				$handle = @fopen($file, 'c');
+
+				if (is_resource($handle))
 				{
+					fclose($handle);
 					return true;
 				}
 			}