diff --git a/wp-mat.php b/wp-mat.php
index bf9ecbe2cb1bbd89ef3a4a96f18c19220427fddc..4d8c3e6c97249a81ea68ff718a97fcc0f4ba40cb 100644
--- a/wp-mat.php
+++ b/wp-mat.php
@@ -26,10 +26,12 @@ 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 (substr($mimetype, 0, 15) === "application/pdf") {
+            return false;
         }
         return true;
     }