diff --git a/wp-mat.php b/wp-mat.php
index 4d8c3e6c97249a81ea68ff718a97fcc0f4ba40cb..af56c19678d4b7029ed7db8a0be718ae80905ecc 100644
--- a/wp-mat.php
+++ b/wp-mat.php
@@ -30,7 +30,8 @@ class WP_Mat {
     function is_supported_mime_type($mimetype) {
         if (substr($mimetype, 0, 6) === "video/") {
             return false;
-        if (substr($mimetype, 0, 15) === "application/pdf") {
+        }
+        if ($mimetype === "application/pdf") {
             return false;
         }
         return true;