diff --git a/stream/mts/psi/helpers.go b/stream/mts/psi/helpers.go
index 42f0c5fd..9beecab4 100644
--- a/stream/mts/psi/helpers.go
+++ b/stream/mts/psi/helpers.go
@@ -132,8 +132,11 @@ func trimTo(d []byte, t byte) []byte {
 // addPadding adds an appropriate amount of padding to a pat or pmt table for
 // addition to an mpegts packet
 func addPadding(d []byte) []byte {
-	for len(d) < PktSize {
-		d = append(d, 0xff)
+	t := make([]byte, PacketSize)
+	copy(t, d)
+	padding := t[len(d):]
+	for i := range padding {
+		padding[i] = 0xff
 	}
 	return d
 }
diff --git a/stream/mts/psi/psi.go b/stream/mts/psi/psi.go
index 4d76110d..09028ba6 100644
--- a/stream/mts/psi/psi.go
+++ b/stream/mts/psi/psi.go
@@ -26,9 +26,8 @@ LICENSE
 
 package psi
 
-// Misc consts
 const (
-	PktSize = 184
+	PacketSize = 184 // packet size of a psi.
 )
 
 // Lengths of section definitions