diff --git a/openflow15/nx_action.go b/openflow15/nx_action.go
index e54a270..f0824b8 100644
--- a/openflow15/nx_action.go
+++ b/openflow15/nx_action.go
@@ -1953,14 +1953,21 @@ func (p *PropTLV) UnmarshalBinary(data []byte) error {
 	return nil
 }
 
+type EncapType uint32
+
+const (
+	Ethernet EncapType = 0
+	Nsh      EncapType = 1<<16 | 0x894f
+)
+
 type NXActionEncapsulate struct {
 	*NXActionHeader
 	HeaderSize uint16
-	HeaderType uint32
+	HeaderType EncapType
 	Property   []PropTLV
 }
 
-func NewNXActionEncapsulate(headerSize uint16, headerType uint32, property []PropTLV) *NXActionEncapsulate {
+func NewNXActionEncapsulate(headerSize uint16, headerType EncapType, property []PropTLV) *NXActionEncapsulate {
 	a := new(NXActionEncapsulate)
 	a.NXActionHeader = NewNxActionHeader(NXAST_RAW_ENCAP)
 	a.Length = 16
@@ -2047,7 +2054,7 @@ func NewNXActionDecapsulate(headerType uint32) *NXActionDecapsulate {
 }
 
 func (a *NXActionDecapsulate) Len() (n uint16) {
-	return a.Length
+	return 16
 }
 
 func (a *NXActionDecapsulate) MarshalBinary() (data []byte, err error) {