diff --git a/lib/PDL/IO/Touchstone.pm b/lib/PDL/IO/Touchstone.pm
index 3f8d2ec..74a39a1 100644
--- a/lib/PDL/IO/Touchstone.pm
+++ b/lib/PDL/IO/Touchstone.pm
@@ -1308,7 +1308,7 @@ sub _to_diagonal
 
 	if (!@dims || (@dims == 1 && $dims[0] == 1))
 	{
-		$ret = zeroes($n_ports,$n_ports);
+		$ret = zeroes($v->type,$n_ports,$n_ports);
 		$ret->diagonal(0,1) .= $v;
 	}
 	elsif (@dims == 1 && $dims[0] == $n_ports)