I've fixed this upstream. I'll try and release this as soon as possible. If you are happy patching, the fix is trivial:
diff --git a/bin/gscan2pdf b/bin/gscan2pdf index 84f1c22..f8b607a 100755 --- a/bin/gscan2pdf +++ b/bin/gscan2pdf @@ -3137,7 +3137,7 @@ sub file_chooser_response_callback { save_djvu( $filename, $list_of_pages ); } when ('tif') { - save_tiff( $filename, $list_of_pages ); + save_tiff( $filename, undef, $list_of_pages ); } when ('txt') { save_text( $filename, $list_of_pages );