diff --git a/C4/Letters.pm b/C4/Letters.pm
index c03da876a8..763a62d7a9 100644
--- a/C4/Letters.pm
+++ b/C4/Letters.pm
@@ -1247,7 +1247,7 @@ sub _add_attachments {
     foreach my $attachment ( @$attachments ) {
         $message->attach(
             Encode::encode( "UTF-8", $attachment->{content} ),
-            content_type => 'application/octet-stream',
+            content_type => $attachment->{type} || 'application/octet-stream',
             name         => $attachment->{filename},
             disposition  => 'attachment',
         );