diff --git a/mkht.php b/mkht.php
index 448fcfd..79d2af2 100755
--- a/mkht.php
+++ b/mkht.php
@@ -101,7 +101,7 @@ foreach($nodes_cache as $node) {
 		continue;
 
 	preg_match('/(?<pagename>[-\w]+)(?:\.(?<lang>[a-z]{2}))?\.md/', $path_parts_src['basename'], $matches);
-	if ($matches['pagename'] === strtoupper($matches['pagename'])) // Ignore uppercase-only filenames (like README.md)
+	if ($matches['pagename'] === strtoupper($matches['pagename']) AND $matches['pagename'] !== strtolower($matches['pagename'])) // Skip uppercase-only filenames (like README.md), but not digit-only (like 404.md)
 		continue;
 
 	$pages[] = $node;
@@ -280,7 +280,7 @@ foreach ($pages as $node) {
 
 	$relative_addr = str_replace(SITE . 'cache/', '', $base_filepath_src . '.html');
 
-	// As of RFC 3151: A URN Namespace for Public Identifiers
+	// According to RFC 3151: A URN Namespace for Public Identifiers
 	$public_id = 'urn:publicid:' . $config['id'] . str_replace('/', '%2F', $relative_addr);
 
 	preg_match('#\<body\>(?<content>.*)\</body\>#s', file_get_contents($base_filepath_target . '.html'), $match);