diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index a6f5319..aaab4cf 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -12,31 +12,22 @@ jobs:
     steps:
     - uses: actions/setup-go@v2
       with:
-        go-version: '^1.18'
+        go-version: '^1.19'
 
     - uses: actions/checkout@v2
 
     - name: Cache protobuf build
       id: protocache
-      uses: actions/cache@v2
+      uses: actions/cache@v3
       with:
-        path: _vendor/protobuf-3.20.0
-        key: protobuf-3.20.0
+        path: _vendor/protobuf-21.12
+        key: protobuf-21.12
 
     - name: Compile protobuf
       if: steps.protocache.outputs.cache-hit != 'true'
       run: |
         sudo apt-get install -y autoconf automake libtool curl make g++ unzip
-
-        mkdir -p _vendor
-        curl -#fsSL https://github.com/protocolbuffers/protobuf/releases/download/v3.20.0/protobuf-all-3.20.0.tar.gz | tar -xzvf - -C _vendor
-
-        cd _vendor/protobuf-3.20.0
-        ./configure
-        make
-        make -C conformance
-        ls -l src/
-        ls -l conformance/
+        ./protobuf.sh
 
     - run: make install && go mod tidy && go mod verify
     - run: git --no-pager diff --exit-code
diff --git a/features/marshal/marshalto.go b/features/marshal/marshalto.go
index 362b996..245f3a5 100644
--- a/features/marshal/marshalto.go
+++ b/features/marshal/marshalto.go
@@ -46,9 +46,8 @@ type marshal struct {
 var _ generator.FeatureGenerator = (*marshal)(nil)
 
 func (p *marshal) GenerateFile(file *protogen.File) bool {
-	proto3 := file.Desc.Syntax() == protoreflect.Proto3
 	for _, message := range file.Messages {
-		p.message(proto3, message)
+		p.message(message)
 	}
 	return p.once
 }
@@ -130,9 +129,9 @@ func (p *marshal) mapField(kvField *protogen.Field, varName string) {
 	}
 }
 
-func (p *marshal) field(proto3, oneof bool, numGen *counter, field *protogen.Field) {
+func (p *marshal) field(oneof bool, numGen *counter, field *protogen.Field) {
 	fieldname := field.GoName
-	nullable := field.Message != nil || (field.Oneof != nil && field.Oneof.Desc.IsSynthetic()) || (!proto3 && !oneof)
+	nullable := field.Message != nil || (!oneof && field.Desc.HasPresence())
 	repeated := field.Desc.Cardinality() == protoreflect.Repeated
 	if repeated {
 		p.P(`if len(m.`, fieldname, `) > 0 {`)
@@ -433,7 +432,7 @@ func (p *marshal) field(proto3, oneof bool, numGen *counter, field *protogen.Fie
 			p.encodeVarint(`len(`, val, `)`)
 			p.encodeKey(fieldNumber, wireType)
 			p.P(`}`)
-		} else if !oneof && proto3 {
+		} else if !oneof && !field.Desc.HasPresence() {
 			p.P(`if len(m.`, fieldname, `) > 0 {`)
 			p.P(`i -= len(m.`, fieldname, `)`)
 			p.P(`copy(dAtA[i:], m.`, fieldname, `)`)
@@ -569,9 +568,9 @@ func (p *marshal) methodMarshal() string {
 	}
 }
 
-func (p *marshal) message(proto3 bool, message *protogen.Message) {
+func (p *marshal) message(message *protogen.Message) {
 	for _, nested := range message.Messages {
-		p.message(proto3, nested)
+		p.message(nested)
 	}
 
 	if message.Desc.IsMapEntry() {
@@ -631,7 +630,7 @@ func (p *marshal) message(proto3 bool, message *protogen.Message) {
 			field := message.Fields[i]
 			oneof := field.Oneof != nil && !field.Oneof.Desc.IsSynthetic()
 			if !oneof {
-				p.field(proto3, false, &numGen, field)
+				p.field(false, &numGen, field)
 			} else {
 				p.P(`if msg, ok := m.`, field.Oneof.GoName, `.(*`, field.GoIdent.GoName, `); ok {`)
 				marshalForwardOneOf("msg")
@@ -663,7 +662,7 @@ func (p *marshal) message(proto3 bool, message *protogen.Message) {
 			field := message.Fields[i]
 			oneof := field.Oneof != nil && !field.Oneof.Desc.IsSynthetic()
 			if !oneof {
-				p.field(proto3, false, &numGen, field)
+				p.field(false, &numGen, field)
 			}
 		}
 	}
@@ -685,7 +684,7 @@ func (p *marshal) message(proto3 bool, message *protogen.Message) {
 		p.P(``)
 		p.P(`func (m *`, ccTypeName, `) `, p.methodMarshalToSizedBuffer(), `(dAtA []byte) (int, error) {`)
 		p.P(`i := len(dAtA)`)
-		p.field(proto3, true, &numGen, field)
+		p.field(true, &numGen, field)
 		p.P(`return len(dAtA) - i, nil`)
 		p.P(`}`)
 	}
diff --git a/features/size/size.go b/features/size/size.go
index 44d0fa1..21fa307 100644
--- a/features/size/size.go
+++ b/features/size/size.go
@@ -34,9 +34,8 @@ func (p *size) Name() string {
 }
 
 func (p *size) GenerateFile(file *protogen.File) bool {
-	proto3 := file.Desc.Syntax() == protoreflect.Proto3
 	for _, message := range file.Messages {
-		p.message(proto3, message)
+		p.message(message)
 	}
 
 	return p.once
@@ -72,9 +71,9 @@ func (p *size) messageSize(varName, sizeName string, message *protogen.Message)
 	}
 }
 
-func (p *size) field(proto3, oneof bool, field *protogen.Field, sizeName string) {
+func (p *size) field(oneof bool, field *protogen.Field, sizeName string) {
 	fieldname := field.GoName
-	nullable := field.Message != nil || (field.Oneof != nil && field.Oneof.Desc.IsSynthetic()) || (!proto3 && !oneof)
+	nullable := field.Message != nil || (!oneof && field.Desc.HasPresence())
 	repeated := field.Desc.Cardinality() == protoreflect.Repeated
 	if repeated {
 		p.P(`if len(m.`, fieldname, `) > 0 {`)
@@ -239,7 +238,7 @@ func (p *size) field(proto3, oneof bool, field *protogen.Field, sizeName string)
 			p.P(`l = len(b)`)
 			p.P(`n+=`, strconv.Itoa(key), `+l+sov(uint64(l))`)
 			p.P(`}`)
-		} else if !oneof && proto3 {
+		} else if !oneof && !field.Desc.HasPresence() {
 			p.P(`l=len(m.`, fieldname, `)`)
 			p.P(`if l > 0 {`)
 			p.P(`n+=`, strconv.Itoa(key), `+l+sov(uint64(l))`)
@@ -276,9 +275,9 @@ func (p *size) field(proto3, oneof bool, field *protogen.Field, sizeName string)
 	}
 }
 
-func (p *size) message(proto3 bool, message *protogen.Message) {
+func (p *size) message(message *protogen.Message) {
 	for _, nested := range message.Messages {
-		p.message(proto3, nested)
+		p.message(nested)
 	}
 
 	if message.Desc.IsMapEntry() {
@@ -300,7 +299,7 @@ func (p *size) message(proto3 bool, message *protogen.Message) {
 	for _, field := range message.Fields {
 		oneof := field.Oneof != nil && !field.Oneof.Desc.IsSynthetic()
 		if !oneof {
-			p.field(proto3, false, field, sizeName)
+			p.field(false, field, sizeName)
 		} else {
 			fieldname := field.Oneof.GoName
 			if _, ok := oneofs[fieldname]; !ok {
@@ -327,7 +326,7 @@ func (p *size) message(proto3 bool, message *protogen.Message) {
 		p.P(`}`)
 		p.P(`var l int`)
 		p.P(`_ = l`)
-		p.field(proto3, true, field, sizeName)
+		p.field(true, field, sizeName)
 		p.P(`return n`)
 		p.P(`}`)
 	}
diff --git a/protobuf.sh b/protobuf.sh
index ca0afee..5f843f7 100755
--- a/protobuf.sh
+++ b/protobuf.sh
@@ -11,14 +11,17 @@ if [ -f "$PROTOBUF_PATH/protoc" ]; then
     exit 0
 fi
 
+mkdir -p _vendor
 curl -sS -L -o "$ROOT/_vendor/pb.tar.gz" http://github.com/protocolbuffers/protobuf/releases/download/v${PROTOBUF_VERSION}/protobuf-all-${PROTOBUF_VERSION}.tar.gz
 
 cd "$ROOT/_vendor"
 tar zxf pb.tar.gz
 
 cd protobuf-${PROTOBUF_VERSION}
-./configure --quiet
+./configure
 make
-cd conformance/ && make
+make -C conformance
 
 echo "Dowloaded and compiled protobuf $PROTOBUF_VERSION to $PROTOBUF_PATH"
+ls -l src/
+ls -l conformance/
diff --git a/testproto/proto3opt/opt_vtproto.pb.go b/testproto/proto3opt/opt_vtproto.pb.go
index 9fd1382..06c1fa5 100644
--- a/testproto/proto3opt/opt_vtproto.pb.go
+++ b/testproto/proto3opt/opt_vtproto.pb.go
@@ -204,13 +204,11 @@ func (m *OptionalFieldInProto3) MarshalToSizedBufferVT(dAtA []byte) (int, error)
 		dAtA[i] = 0x80
 	}
 	if m.OptionalBytes != nil {
-		if len(m.OptionalBytes) > 0 {
-			i -= len(m.OptionalBytes)
-			copy(dAtA[i:], m.OptionalBytes)
-			i = encodeVarint(dAtA, i, uint64(len(m.OptionalBytes)))
-			i--
-			dAtA[i] = 0x7a
-		}
+		i -= len(m.OptionalBytes)
+		copy(dAtA[i:], m.OptionalBytes)
+		i = encodeVarint(dAtA, i, uint64(len(m.OptionalBytes)))
+		i--
+		dAtA[i] = 0x7a
 	}
 	if m.OptionalString != nil {
 		i -= len(*m.OptionalString)
@@ -347,13 +345,11 @@ func (m *OptionalFieldInProto3) MarshalToSizedBufferVTStrict(dAtA []byte) (int,
 		dAtA[i] = 0x80
 	}
 	if m.OptionalBytes != nil {
-		if len(m.OptionalBytes) > 0 {
-			i -= len(m.OptionalBytes)
-			copy(dAtA[i:], m.OptionalBytes)
-			i = encodeVarint(dAtA, i, uint64(len(m.OptionalBytes)))
-			i--
-			dAtA[i] = 0x7a
-		}
+		i -= len(m.OptionalBytes)
+		copy(dAtA[i:], m.OptionalBytes)
+		i = encodeVarint(dAtA, i, uint64(len(m.OptionalBytes)))
+		i--
+		dAtA[i] = 0x7a
 	}
 	if m.OptionalString != nil {
 		i -= len(*m.OptionalString)
@@ -492,9 +488,7 @@ func (m *OptionalFieldInProto3) SizeVT() (n int) {
 	}
 	if m.OptionalBytes != nil {
 		l = len(m.OptionalBytes)
-		if l > 0 {
-			n += 1 + l + sov(uint64(l))
-		}
+		n += 1 + l + sov(uint64(l))
 	}
 	if m.OptionalEnum != nil {
 		n += 2 + sov(uint64(*m.OptionalEnum))
diff --git a/testproto/proto3opt/proto3opt_test.go b/testproto/proto3opt/proto3opt_test.go
new file mode 100644
index 0000000..90e058b
--- /dev/null
+++ b/testproto/proto3opt/proto3opt_test.go
@@ -0,0 +1,30 @@
+package proto3opt
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+	"google.golang.org/protobuf/proto"
+)
+
+func TestEmptyBytesMarshalling(t *testing.T) {
+	a := &OptionalFieldInProto3{
+		OptionalBytes: nil,
+	}
+	b := &OptionalFieldInProto3{
+		OptionalBytes: []byte{},
+	}
+
+	type Message interface {
+		proto.Message
+		MarshalVT() ([]byte, error)
+	}
+
+	for _, msg := range []Message{a, b} {
+		vt, err := msg.MarshalVT()
+		require.NoError(t, err)
+		goog, err := proto.Marshal(msg)
+		require.NoError(t, err)
+		require.Equal(t, goog, vt)
+	}
+}