diff --git a/min/lib/Minify/HTML/Helper.php b/min/lib/Minify/HTML/Helper.php
index f4808c5..59d06dc 100644
--- a/min/lib/Minify/HTML/Helper.php
+++ b/min/lib/Minify/HTML/Helper.php
@@ -17,7 +17,7 @@ class Minify_HTML_Helper {
 
     /**
      * Get an HTML-escaped Minify URI for a group or set of files
-     * 
+     *
      * @param string|array $keyOrFiles a group key or array of filepaths/URIs
      * @param array $opts options:
      *   'farExpires' : (default true) append a modified timestamp for cache revving
@@ -141,7 +141,7 @@ class Minify_HTML_Helper {
         $max = $lastModified;
         /** @var Minify_Source $source */
         foreach ((array)$sources as $source) {
-            if ($source instanceof Minify_Source && $source->getLastModified() !== null) {
+            if ($source instanceof Minify_Source) {
                 $max = max($max, $source->getLastModified());
             } elseif (is_object($source) && isset($source->lastModified)) {
                 $max = max($max, $source->lastModified);
@@ -161,7 +161,7 @@ class Minify_HTML_Helper {
     protected $_filePaths = array();
     protected $_lastModified = null;
 
-    
+
     /**
      * In a given array of strings, find the character they all have at
      * a particular index
@@ -208,7 +208,7 @@ class Minify_HTML_Helper {
         }
         $base = preg_replace('@[^/]+$@', '', $base);
         $uri = $minRoot . 'f=' . implode(',', $paths);
-        
+
         if (substr($base, -1) === '/') {
             // we have a base dir!
             $basedPaths = $paths;