diff --git a/kmreaderwin.cpp b/kmreaderwin.cpp
index b0c3d845f..679fe04fd 100644
--- a/kmreaderwin.cpp
+++ b/kmreaderwin.cpp
@@ -2443,7 +2443,7 @@ void KMReaderWin::openAttachment( int id, const QString & name )
   if ( KMail::Util::handleUrlOnMac( mAtmCurrentName ) )
     return;
 
-  if ( mimetype.isNull() ) {
+  if ( mimetype.isNull() || mimetype->name() == "application/octet-stream" ) {
     // consider the filename if mimetype can not be found by content-type
     mimetype = KMimeType::findByPath( name, 0, true /* no disk access */ );
   }