Index: files.php
===================================================================
--- files.php	(revision 1755)
+++ files.php	(working copy)
@@ -185,11 +185,11 @@
 $db->query("UPDATE ".X_PREFIX."attachments SET downloads=downloads+1 WHERE aid=$aid");
 
 // Set response headers
-$type = strtolower($file['filetype']);
-$type = ($type == 'text/html') ? 'text/plain' : $type;
 if ($file['img_size'] == '') {
+    $type = 'application/binary';
     $dispositionType = 'attachment';
 } else {
+    $type = strtolower($file['filetype']);
     $dispositionType = 'inline';
 }
 

Index: viewthread.php
===================================================================
--- viewthread.php	(revision 1756)
+++ viewthread.php	(working copy)
@@ -691,9 +691,8 @@
         error($lang['filecorrupt']);
     }
 
-    $type = strtolower($file['filetype']);
     $size = (int) $file['filesize'];
-    $type = ($type == 'text/html') ? 'text/plain' : $type;
+    $type = 'application/binary';
 
     header("Content-type: $type");
     header("Content-length: $size");