diff --git a/wp-mat.php b/wp-mat.php
index bf9ecbe2cb1bbd89ef3a4a96f18c19220427fddc..af56c19678d4b7029ed7db8a0be718ae80905ecc 100644
--- a/wp-mat.php
+++ b/wp-mat.php
@@ -26,11 +26,14 @@ class WP_Mat {
 
     // Check if the mime type is one of those we want to clean up.
     // Use a blacklist, currently empty. Send everything by default
-    // except video.
+    // except video, and pdf.
     function is_supported_mime_type($mimetype) {
         if (substr($mimetype, 0, 6) === "video/") {
             return false;
         }
+        if ($mimetype === "application/pdf") {
+            return false;
+        }
         return true;
     }