diff --git a/scte35/scte35.go b/scte35/scte35.go
index 4c42e0a..fd8c590 100644
--- a/scte35/scte35.go
+++ b/scte35/scte35.go
@@ -225,7 +225,8 @@ func (s *scte35) Data() []byte {
 }
 
 func uint40(buf []byte) gots.PTS {
-	return (gots.PTS(buf[0]&0x1) << 32) | (gots.PTS(buf[1]) << 24) | (gots.PTS(buf[2]) << 16) | (gots.PTS(buf[3]) << 8) | (gots.PTS(buf[4]))
+	data := append([]byte{0, 0, 0}, buf[:5]...)
+	return gots.PTS(binary.BigEndian.Uint64(data))
 }
 
 // String returns a string representation of the SCTE35 message.
diff --git a/scte35/segmentationdescriptor_test.go b/scte35/segmentationdescriptor_test.go
index 69bff3f..28c2f33 100644
--- a/scte35/segmentationdescriptor_test.go
+++ b/scte35/segmentationdescriptor_test.go
@@ -54,7 +54,7 @@ var network_end = []byte{
 var program_start = []byte{
 	0x00, 0xfc, 0x30, 0x35, 0x00, 0x00, 0x00, 0x02, 0xdd, 0x20, 0x00, 0x00, 0x00, 0x05, 0x06, 0xfe,
 	0x00, 0x02, 0xbf, 0xd4, 0x00, 0x1f, 0x02, 0x1d, 0x43, 0x55, 0x45, 0x49, 0x00, 0x00, 0x00, 0x02,
-	0x7f, 0xff, 0x00, 0x09, 0xa7, 0xec, 0x80, 0x09, 0x09, 0x50, 0x72, 0x6f, 0x67, 0x53, 0x74, 0x61,
+	0x7f, 0xff, 0xff, 0x09, 0xa7, 0xec, 0x80, 0x09, 0x09, 0x50, 0x72, 0x6f, 0x67, 0x53, 0x74, 0x61,
 	0x72, 0x74, 0x10, 0x01, 0x01, 0xfd, 0xbe, 0x65, 0x8c,
 }
 
@@ -270,3 +270,20 @@ func TestVSSSignalId(t *testing.T) {
 		t.FailNow()
 	}
 }
+
+func TestSegmentationDuration(t *testing.T) {
+	// Create a 0x10 (program start)
+	programStart, err := NewSCTE35(program_start)
+	if err != nil {
+		t.Error("NewSCTE35(program_start) returned err:", err.Error())
+		t.FailNow()
+	}
+
+	seg := programStart.Descriptors()[0].(*segmentationDescriptor)
+	seg.SetHasDuration(true)
+
+	// segmentation duration supports up to 40 bits
+	if expected, actual := uint64(0xff09a7ec80), uint64(seg.Duration()); expected != actual {
+		t.Errorf("Expected segmentation duraiont to be %v, but %v is found", expected, actual)
+	}
+}