diff --git a/VERSION b/VERSION
index 9beb74d..288adf5 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-0.13.2
+0.13.3
diff --git a/generated/classidmap.go b/generated/classidmap.go
index 7538d66..2fe9ea1 100644
--- a/generated/classidmap.go
+++ b/generated/classidmap.go
@@ -23,8 +23,6 @@
 
 package generated
 
-import "fmt"
-
 // ManagedEntityInfo provides ManagedEntity information
 type ManagedEntityInfo struct {
 	New func(params ...ParamData) (*ManagedEntity, error)
@@ -239,12 +237,13 @@
 // LoadManagedEntityDefinition returns a function to create a Managed Entity for a specific
 // Managed Entity class ID
 func LoadManagedEntityDefinition(classID ClassID, params ...ParamData) (*ManagedEntity, OmciErrors) {
-	newFunc, ok := classToManagedEntityMap[classID]
-	if ok {
+	if newFunc, ok := classToManagedEntityMap[classID]; ok {
 		return newFunc(params...)
 	}
-	return nil, NewUnknownEntityError(fmt.Sprintf("managed entity %d (%#x) definition not found",
-		uint16(classID), uint16(classID)))
+	if IsVendorSpecificClassID(classID) {
+		return NewUnknownVendorSpecificME(classID, params...)
+	}
+	return NewUnknownG988ME(classID, params...)
 }
 
 // GetSupportedClassIDs returns an array of Managed Entity Class IDs supported
@@ -264,3 +263,12 @@
 	}
 	return medef.GetAttributeDefinitions(), err
 }
+
+// IsVendorSpecificClassID returns true if the provided class ID is reserved in ITU-T G.988
+// for vendor specific functionality
+func IsVendorSpecificClassID(classID ClassID) bool {
+	// Values below are from Table 11.2.4-1 of ITU-T G.988 (11/2017)
+	return (ClassID(240) <= classID && classID <= ClassID(255)) ||
+		(ClassID(350) <= classID && classID <= ClassID(399)) ||
+		(ClassID(65280) <= classID && classID <= ClassID(65535))
+}
\ No newline at end of file
diff --git a/generated/classsupport.go b/generated/classsupport.go
index 5edba61..9cc9dc6 100644
--- a/generated/classsupport.go
+++ b/generated/classsupport.go
@@ -26,6 +26,10 @@
 	Unsupported        // OMCI returns error code if accessed
 	PartiallySupported // some aspects of ME supported
 	Ignored            // OMCI supported, but underlying function is now
+
+	// The following two are specific unsupported Managed Entity Definitions
+	UnsupportedManagedEntity				// Unsupported ITU G.988 Class ID
+	UnsupportedVendorSpecificManagedEntity	// Unsupported Vendor Specific Class ID
 )
 
 func (cs ClassSupport) String() string {
diff --git a/generated/me.go b/generated/me.go
index 7e51f85..caa32bc 100644
--- a/generated/me.go
+++ b/generated/me.go
@@ -74,6 +74,11 @@
 	return entity.definition.GetClassID()
 }
 
+// SetClassID assigns the 16-bit class ID of a Managed Entity
+func (entity *ManagedEntity) SetClassID(classID ClassID) {
+	entity.definition.SetClassID(classID)
+}
+
 // GetMessageTypes returns the OMCI message types that a Managed Entity supports
 func (entity ManagedEntity) GetMessageTypes() mapset.Set {
 	return entity.definition.GetMessageTypes()
diff --git a/generated/medef.go b/generated/medef.go
index a2bd2da..7cb85d2 100644
--- a/generated/medef.go
+++ b/generated/medef.go
@@ -58,6 +58,11 @@
 	return bme.ClassID
 }
 
+// SetClassID assigns the 16-bit class ID of a managed entity from a ME Definition
+func (bme *ManagedEntityDefinition) SetClassID(classID ClassID) {
+	bme.ClassID = classID
+}
+
 // GetMessageTypes retrieves the OMCI Message Types supporte3d by a managed entity from a ME Definition
 func (bme ManagedEntityDefinition) GetMessageTypes() mapset.Set {
 	return bme.MessageTypes
diff --git a/generated/unknowng988me.go b/generated/unknowng988me.go
new file mode 100644
index 0000000..af68823
--- /dev/null
+++ b/generated/unknowng988me.go
@@ -0,0 +1,90 @@
+/*
+ * Copyright (c) 2018 - present.  Boling Consulting Solutions (bcsw.net)
+ * Copyright 2020-present Open Networking Foundation
+
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+
+ * http://www.apache.org/licenses/LICENSE-2.0
+
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+/*
+ * NOTE: This file was generated, manual edits will be overwritten!
+ *
+ * Generated by 'goCodeGenerator.py':
+ *              https://github.com/cboling/OMCI-parser/README.md
+ */
+
+package generated
+
+import "github.com/deckarep/golang-set"
+
+
+var unknownG988BME *ManagedEntityDefinition
+
+type UnknownG988ME struct {
+	ManagedEntityDefinition
+	Attributes AttributeValueMap
+}
+
+func init() {
+	unknownG988BME = &ManagedEntityDefinition{
+		Name:    "UnknownItuG988ManagedEntity",
+		ClassID: 0,
+		MessageTypes: mapset.NewSetWith(
+			MibUploadNext,
+			AlarmNotification,
+			AttributeValueChange,
+		),
+		AllowedAttributeMask: 0xffff,
+		AttributeDefinitions: AttributeDefinitionMap{
+			0: Uint16Field("ManagedEntityId", PointerAttributeType, 0x0000, 0, mapset.NewSetWith(Read), false, false, false, 0),
+			1: MultiByteField("UnknownAttr_1", OctetsAttributeType, 0x8000, 1, toOctets("AA=="), mapset.NewSetWith(Read), true, true, false, 1),
+			2: MultiByteField("UnknownAttr_2", OctetsAttributeType, 0x4000, 1, toOctets("AA=="), mapset.NewSetWith(Read), true, true, false, 2),
+			3: MultiByteField("UnknownAttr_3", OctetsAttributeType, 0x2000, 1, toOctets("AA=="), mapset.NewSetWith(Read), true, true, false, 3),
+			4: MultiByteField("UnknownAttr_4", OctetsAttributeType, 0x1000, 1, toOctets("AA=="), mapset.NewSetWith(Read), true, true, false, 4),
+			5: MultiByteField("UnknownAttr_5", OctetsAttributeType, 0x0800, 1, toOctets("AA=="), mapset.NewSetWith(Read), true, true, false, 5),
+			6: MultiByteField("UnknownAttr_6", OctetsAttributeType, 0x0400, 1, toOctets("AA=="), mapset.NewSetWith(Read), true, true, false, 6),
+			7: MultiByteField("UnknownAttr_7", OctetsAttributeType, 0x0200, 1, toOctets("AA=="), mapset.NewSetWith(Read), true, true, false, 7),
+			8: MultiByteField("UnknownAttr_8", OctetsAttributeType, 0x0100, 1, toOctets("AA=="), mapset.NewSetWith(Read), true, true, false, 8),
+			9: MultiByteField("UnknownAttr_9", OctetsAttributeType, 0x0080, 1, toOctets("AA=="), mapset.NewSetWith(Read), true, true, false, 9),
+			10: MultiByteField("UnknownAttr_10", OctetsAttributeType, 0x0040, 1, toOctets("AA=="), mapset.NewSetWith(Read), true, true, false, 10),
+			11: MultiByteField("UnknownAttr_11", OctetsAttributeType, 0x0020, 1, toOctets("AA=="), mapset.NewSetWith(Read), true, true, false, 11),
+			12: MultiByteField("UnknownAttr_12", OctetsAttributeType, 0x0010, 1, toOctets("AA=="), mapset.NewSetWith(Read), true, true, false, 12),
+			13: MultiByteField("UnknownAttr_13", OctetsAttributeType, 0x0008, 1, toOctets("AA=="), mapset.NewSetWith(Read), true, true, false, 13),
+			14: MultiByteField("UnknownAttr_14", OctetsAttributeType, 0x0004, 1, toOctets("AA=="), mapset.NewSetWith(Read), true, true, false, 14),
+			15: MultiByteField("UnknownAttr_15", OctetsAttributeType, 0x0002, 1, toOctets("AA=="), mapset.NewSetWith(Read), true, true, false, 15),
+			16: MultiByteField("UnknownAttr_16", OctetsAttributeType, 0x0001, 1, toOctets("AA=="), mapset.NewSetWith(Read), true, true, false, 16),
+		},
+		Access:  UnknownAccess,
+		Support: UnsupportedManagedEntity,
+	}
+}
+
+func NewUnknownG988ME(classID ClassID, params ...ParamData) (*ManagedEntity, OmciErrors) {
+	return newUnknownManagedEntity(classID, *unknownG988BME, params...)
+}
+
+// newUnknownManagedEntity creates a ManagedEntity given an ME Definition and parameter/attribute data
+// much like NewManagedEntity but treats attributes is a special way
+func newUnknownManagedEntity(classID ClassID, definition ManagedEntityDefinition, params ...ParamData) (*ManagedEntity, OmciErrors) {
+	entity := &ManagedEntity{
+		definition: definition,
+		attributes: make(map[string]interface{}),
+	}
+	// Make this unique for the received class ID and attribute masks
+	entity.SetClassID(classID)
+
+	if params != nil {
+		if err := entity.setAttributes(params...); err.StatusCode() != Success {
+			return nil, err
+		}
+	}
+	return entity, NewOmciSuccess()
+}
diff --git a/generated/unknownvendorspecificme.go b/generated/unknownvendorspecificme.go
new file mode 100644
index 0000000..146e012
--- /dev/null
+++ b/generated/unknownvendorspecificme.go
@@ -0,0 +1,72 @@
+/*
+ * Copyright (c) 2018 - present.  Boling Consulting Solutions (bcsw.net)
+ * Copyright 2020-present Open Networking Foundation
+
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+
+ * http://www.apache.org/licenses/LICENSE-2.0
+
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+ /*
+ * NOTE: This file was generated, manual edits will be overwritten!
+ *
+ * Generated by 'goCodeGenerator.py':
+ *              https://github.com/cboling/OMCI-parser/README.md
+ */
+
+package generated
+
+import "github.com/deckarep/golang-set"
+
+
+var unknownVendorSpecificBME *ManagedEntityDefinition
+
+type UnknownVendorSpecific struct {
+	ManagedEntityDefinition
+	Attributes AttributeValueMap
+}
+
+func init() {
+	unknownVendorSpecificBME = &ManagedEntityDefinition{
+		Name:    "UnknownVendorSpecificManagedEntity",
+		ClassID: 0,
+		MessageTypes: mapset.NewSetWith(
+			MibUploadNext,
+			AlarmNotification,
+			AttributeValueChange,
+		),
+		AllowedAttributeMask: 0xffff,
+		AttributeDefinitions: AttributeDefinitionMap{
+			0: Uint16Field("ManagedEntityId", PointerAttributeType, 0x0000, 0, mapset.NewSetWith(Read), false, false, false, 0),
+			1: MultiByteField("UnknownAttr_1", OctetsAttributeType, 0x8000, 1, toOctets("AA=="), mapset.NewSetWith(Read), true, true, false, 1),
+			2: MultiByteField("UnknownAttr_2", OctetsAttributeType, 0x4000, 1, toOctets("AA=="), mapset.NewSetWith(Read), true, true, false, 2),
+			3: MultiByteField("UnknownAttr_3", OctetsAttributeType, 0x2000, 1, toOctets("AA=="), mapset.NewSetWith(Read), true, true, false, 3),
+			4: MultiByteField("UnknownAttr_4", OctetsAttributeType, 0x1000, 1, toOctets("AA=="), mapset.NewSetWith(Read), true, true, false, 4),
+			5: MultiByteField("UnknownAttr_5", OctetsAttributeType, 0x0800, 1, toOctets("AA=="), mapset.NewSetWith(Read), true, true, false, 5),
+			6: MultiByteField("UnknownAttr_6", OctetsAttributeType, 0x0400, 1, toOctets("AA=="), mapset.NewSetWith(Read), true, true, false, 6),
+			7: MultiByteField("UnknownAttr_7", OctetsAttributeType, 0x0200, 1, toOctets("AA=="), mapset.NewSetWith(Read), true, true, false, 7),
+			8: MultiByteField("UnknownAttr_8", OctetsAttributeType, 0x0100, 1, toOctets("AA=="), mapset.NewSetWith(Read), true, true, false, 8),
+			9: MultiByteField("UnknownAttr_9", OctetsAttributeType, 0x0080, 1, toOctets("AA=="), mapset.NewSetWith(Read), true, true, false, 9),
+			10: MultiByteField("UnknownAttr_10", OctetsAttributeType, 0x0040, 1, toOctets("AA=="), mapset.NewSetWith(Read), true, true, false, 10),
+			11: MultiByteField("UnknownAttr_11", OctetsAttributeType, 0x0020, 1, toOctets("AA=="), mapset.NewSetWith(Read), true, true, false, 11),
+			12: MultiByteField("UnknownAttr_12", OctetsAttributeType, 0x0010, 1, toOctets("AA=="), mapset.NewSetWith(Read), true, true, false, 12),
+			13: MultiByteField("UnknownAttr_13", OctetsAttributeType, 0x0008, 1, toOctets("AA=="), mapset.NewSetWith(Read), true, true, false, 13),
+			14: MultiByteField("UnknownAttr_14", OctetsAttributeType, 0x0004, 1, toOctets("AA=="), mapset.NewSetWith(Read), true, true, false, 14),
+			15: MultiByteField("UnknownAttr_15", OctetsAttributeType, 0x0002, 1, toOctets("AA=="), mapset.NewSetWith(Read), true, true, false, 15),
+			16: MultiByteField("UnknownAttr_16", OctetsAttributeType, 0x0001, 1, toOctets("AA=="), mapset.NewSetWith(Read), true, true, false, 16),
+		},
+		Access:  UnknownAccess,
+		Support: UnsupportedVendorSpecificManagedEntity,
+	}
+}
+
+func NewUnknownVendorSpecificME(classID ClassID, params ...ParamData) (*ManagedEntity, OmciErrors) {
+	return newUnknownManagedEntity(classID, *unknownVendorSpecificBME, params...)
+}
diff --git a/omci_test.go b/omci_test.go
index 1a8105c..12575d7 100644
--- a/omci_test.go
+++ b/omci_test.go
@@ -1079,3 +1079,170 @@
 //		firstTid += 1
 //	}
 //}
+
+// TestUnsupportedG988ClassIDMibUploadNextResponse tests decoding of an Unknown class ID that is
+// in the range of IDs assigned for G.988 use
+func TestUnsupportedG988ClassIDMibUploadNextResponse(t *testing.T) {
+	// The unsupported G.988 class ID below is 37 (0x0025), which is marked in the G.988
+	// (11/2017) as 'Intentionally left blank).  The encoded frame is a Get-Next
+	// response with a single attribute 1 & 16 (0x8001) encoded.
+	//
+	tid := 3
+	cid := 0x25
+	eid := 1
+	mask := 0x8000
+	hdr := "00032e0a00020000002500018000"
+	trailer := "0000002828ce00e2"
+	attr := "0102030405060708090A0B0C0D0E0F101112131415161718191A"
+	msg := hdr + attr + trailer
+	data, err := stringToPacket(msg)
+	assert.NoError(t, err)
+
+	packet := gopacket.NewPacket(data, LayerTypeOMCI, gopacket.NoCopy)
+	assert.NotNil(t, packet)
+
+	omciLayer := packet.Layer(LayerTypeOMCI)
+	assert.NotNil(t, packet)
+
+	omciMsg, ok := omciLayer.(*OMCI)
+	assert.True(t, ok)
+	assert.Equal(t, omciMsg.TransactionID, uint16(tid))
+	assert.Equal(t, omciMsg.MessageType, MibUploadNextResponseType)
+	assert.Equal(t, omciMsg.Length, uint16(40))
+
+	msgLayer := packet.Layer(LayerTypeMibUploadNextResponse)
+	assert.NotNil(t, msgLayer)
+
+	uploadResponse, ok2 := msgLayer.(*MibUploadNextResponse)
+	assert.True(t, ok2)
+	assert.NotNil(t, uploadResponse)
+	assert.Equal(t, uploadResponse.EntityClass, OnuDataClassID)
+	assert.Equal(t, uploadResponse.EntityInstance, uint16(0))
+	assert.Equal(t, uploadResponse.ReportedME.GetClassID(), ClassID(cid))
+	assert.Equal(t, uploadResponse.ReportedME.GetEntityID(), uint16(eid))
+	assert.Equal(t, uploadResponse.ReportedME.GetAttributeMask(), uint16(mask))
+
+	name := "UnknownAttr_1"
+	blobAttribute, err := uploadResponse.ReportedME.GetAttribute(name)
+
+	assert.Nil(t, err)
+	assert.NotNil(t, blobAttribute)
+
+	byteValue, ok3 := blobAttribute.([]uint8)
+	assert.True(t, ok3)
+	assert.NotNil(t, byteValue)
+}
+
+
+func TestUnsupportedG988ClassIDMibUploadNextResponseAttributes(t *testing.T) {
+	// Same as previous, but try different attribute mask combinations
+	tid := 3
+	cid := 0x25
+	eid := 1
+
+	// There are a number of ranges for vendor ID use. List below picks one from
+	// each of those ranges
+	masks := []uint16{0x8001, 0x0000, 0x0001, 0x8000}
+
+	trailer := "0000002828ce00e2"
+	attr := "0102030405060708090A0B0C0D0E0F101112131415161718191A"
+
+	for _, mask := range masks {
+		hdr := fmt.Sprintf("00032e0a0002000000250001%04x", mask)
+
+		msg := hdr + attr + trailer
+		data, err := stringToPacket(msg)
+		assert.NoError(t, err)
+
+		packet := gopacket.NewPacket(data, LayerTypeOMCI, gopacket.NoCopy)
+		assert.NotNil(t, packet)
+
+		omciLayer := packet.Layer(LayerTypeOMCI)
+		assert.NotNil(t, packet)
+
+		omciMsg, ok := omciLayer.(*OMCI)
+		assert.True(t, ok)
+		assert.Equal(t, omciMsg.TransactionID, uint16(tid))
+		assert.Equal(t, omciMsg.MessageType, MibUploadNextResponseType)
+		assert.Equal(t, omciMsg.Length, uint16(40))
+
+		msgLayer := packet.Layer(LayerTypeMibUploadNextResponse)
+		assert.NotNil(t, msgLayer)
+
+		uploadResponse, ok2 := msgLayer.(*MibUploadNextResponse)
+		assert.True(t, ok2)
+		assert.NotNil(t, uploadResponse)
+		assert.Equal(t, uploadResponse.EntityClass, OnuDataClassID)
+		assert.Equal(t, uploadResponse.EntityInstance, uint16(0))
+		assert.Equal(t, uploadResponse.ReportedME.GetClassID(), ClassID(cid))
+		assert.Equal(t, uploadResponse.ReportedME.GetEntityID(), uint16(eid))
+		assert.Equal(t, uploadResponse.ReportedME.GetAttributeMask(), uint16(mask))
+
+		//name := "UnknownAttr_1"
+		//blobAttribute, err := uploadResponse.ReportedME.GetAttribute(name)
+		//
+		//assert.Nil(t, err)
+		//assert.NotNil(t, blobAttribute)
+		//
+		//byteValue, ok3 := blobAttribute.([]uint8)
+		//assert.True(t, ok3)
+		//assert.NotNil(t, byteValue)
+	}
+}
+
+// TestUnsupportedVendorClassIDMibUploadNextResponse tests decoding of an Unknown class ID that is
+// in the range of IDs assigned for vendor assignment
+func TestUnsupportedVendorClassIDMibUploadNextResponse(t *testing.T) {
+	tid := 3
+	eid := 0
+	mask := 0x8000
+
+	// There are a number of ranges for vendor ID use. List below picks one from
+	// each of those ranges
+	classIDs := []uint16{250, 355, 65500}
+
+	hdr := "00032e0a00020000"
+	attr := "0102030405060708090A0B0C0D0E0F101112131415161718191A"
+	trailer := "0000002828ce00e2"
+
+	for _, cid := range classIDs {
+		cidToMask := fmt.Sprintf("%04x%04x%04x", cid, eid, mask)
+		msg := hdr + cidToMask + attr + trailer
+		data, err := stringToPacket(msg)
+		assert.NoError(t, err)
+
+		packet := gopacket.NewPacket(data, LayerTypeOMCI, gopacket.NoCopy)
+		assert.NotNil(t, packet)
+
+		omciLayer := packet.Layer(LayerTypeOMCI)
+		assert.NotNil(t, packet)
+
+		omciMsg, ok := omciLayer.(*OMCI)
+		assert.True(t, ok)
+		assert.Equal(t, omciMsg.TransactionID, uint16(tid))
+		assert.Equal(t, omciMsg.MessageType, MibUploadNextResponseType)
+		assert.Equal(t, omciMsg.Length, uint16(40))
+
+		msgLayer := packet.Layer(LayerTypeMibUploadNextResponse)
+		assert.NotNil(t, msgLayer)
+
+		uploadResponse, ok2 := msgLayer.(*MibUploadNextResponse)
+		assert.True(t, ok2)
+		assert.NotNil(t, uploadResponse)
+		assert.Equal(t, uploadResponse.EntityClass, OnuDataClassID)
+		assert.Equal(t, uploadResponse.EntityInstance, uint16(0))
+		assert.Equal(t, uploadResponse.ReportedME.GetClassID(), ClassID(cid))
+		assert.Equal(t, uploadResponse.ReportedME.GetEntityID(), uint16(eid))
+		assert.Equal(t, uploadResponse.ReportedME.GetAttributeMask(), uint16(mask))
+
+		name := "UnknownAttr_1"
+		blobAttribute, err := uploadResponse.ReportedME.GetAttribute(name)
+
+		assert.Nil(t, err)
+		assert.NotNil(t, blobAttribute)
+
+		byteValue, ok3 := blobAttribute.([]uint8)
+		assert.True(t, ok3)
+		assert.NotNil(t, byteValue)
+	}
+}
\ No newline at end of file