diff --git a/bool.go b/bool.go
index b0d0432..fbc6f2b 100644
--- a/bool.go
+++ b/bool.go
@@ -1,5 +1,5 @@
 // Code generated by go generate
-// This file was generated by robots at 2018-11-14 00:52:25.812586 +0000 UTC
+// This file was generated by robots at 2018-12-06 14:29:53.447681 +0000 UTC
 
 package optional
 
@@ -56,11 +56,16 @@ func (b Bool) MarshalJSON() ([]byte, error) {
 	if b.Present() {
 		return json.Marshal(b.value)
 	}
-	var zero bool
-	return json.Marshal(zero)
+	return json.Marshal(nil)
 }
 
 func (b *Bool) UnmarshalJSON(data []byte) error {
+
+	if string(data) == "null" {
+		b.value = nil
+		return nil
+	}
+
 	var value bool
 
 	if err := json.Unmarshal(data, &value); err != nil {
diff --git a/byte.go b/byte.go
index d73e356..39409d8 100644
--- a/byte.go
+++ b/byte.go
@@ -1,5 +1,5 @@
 // Code generated by go generate
-// This file was generated by robots at 2018-11-14 00:52:26.274563 +0000 UTC
+// This file was generated by robots at 2018-12-06 14:29:53.79355 +0000 UTC
 
 package optional
 
@@ -56,11 +56,16 @@ func (b Byte) MarshalJSON() ([]byte, error) {
 	if b.Present() {
 		return json.Marshal(b.value)
 	}
-	var zero byte
-	return json.Marshal(zero)
+	return json.Marshal(nil)
 }
 
 func (b *Byte) UnmarshalJSON(data []byte) error {
+
+	if string(data) == "null" {
+		b.value = nil
+		return nil
+	}
+
 	var value byte
 
 	if err := json.Unmarshal(data, &value); err != nil {
diff --git a/cmd/optional/main.go b/cmd/optional/main.go
index 54b9dbe..0c8ce56 100644
--- a/cmd/optional/main.go
+++ b/cmd/optional/main.go
@@ -183,11 +183,16 @@ func ({{ .VariableName }} {{ .OutputName }}) MarshalJSON() ([]byte, error) {
 	if {{ .VariableName }}.Present() {
 		return json.Marshal({{ .VariableName }}.value)
 	}
-	var zero {{ .TypeName }}
-	return json.Marshal(zero)
+	return json.Marshal(nil)
 }
 
 func ({{ .VariableName }} *{{ .OutputName }}) UnmarshalJSON(data []byte) error {
+
+	if string(data) == "null" {
+		{{ .VariableName }}.value = nil
+		return nil
+	}
+
 	var value {{ .TypeName }}
 
 	if err := json.Unmarshal(data, &value); err != nil {
diff --git a/cmd/optional/testdata/optional_bar.go b/cmd/optional/testdata/optional_bar.go
index 20ff0c8..01c9307 100644
--- a/cmd/optional/testdata/optional_bar.go
+++ b/cmd/optional/testdata/optional_bar.go
@@ -1,5 +1,5 @@
 // Code generated by go generate
-// This file was generated by robots at 2018-11-14 00:54:14.621363 +0000 UTC
+// This file was generated by robots at 2018-12-06 17:57:17.641444 +0000 UTC
 
 package bar
 
@@ -56,11 +56,16 @@ func (o optionalBar) MarshalJSON() ([]byte, error) {
 	if o.Present() {
 		return json.Marshal(o.value)
 	}
-	var zero bar
-	return json.Marshal(zero)
+	return json.Marshal(nil)
 }
 
 func (o *optionalBar) UnmarshalJSON(data []byte) error {
+
+	if string(data) == "null" {
+		o.value = nil
+		return nil
+	}
+
 	var value bar
 
 	if err := json.Unmarshal(data, &value); err != nil {
diff --git a/cmd/optional/testdata/optional_foo.go b/cmd/optional/testdata/optional_foo.go
index 667a74e..18a2c24 100644
--- a/cmd/optional/testdata/optional_foo.go
+++ b/cmd/optional/testdata/optional_foo.go
@@ -1,5 +1,5 @@
 // Code generated by go generate
-// This file was generated by robots at 2018-11-14 00:54:14.61916 +0000 UTC
+// This file was generated by robots at 2018-12-06 17:57:17.640425 +0000 UTC
 
 package foo
 
@@ -56,11 +56,16 @@ func (o OptionalFoo) MarshalJSON() ([]byte, error) {
 	if o.Present() {
 		return json.Marshal(o.value)
 	}
-	var zero Foo
-	return json.Marshal(zero)
+	return json.Marshal(nil)
 }
 
 func (o *OptionalFoo) UnmarshalJSON(data []byte) error {
+
+	if string(data) == "null" {
+		o.value = nil
+		return nil
+	}
+
 	var value Foo
 
 	if err := json.Unmarshal(data, &value); err != nil {
diff --git a/cmd/optional/testdata/string.go b/cmd/optional/testdata/string.go
index 44e2117..64074b9 100644
--- a/cmd/optional/testdata/string.go
+++ b/cmd/optional/testdata/string.go
@@ -1,5 +1,5 @@
 // Code generated by go generate
-// This file was generated by robots at 2018-11-14 00:54:14.615858 +0000 UTC
+// This file was generated by robots at 2018-12-06 17:57:17.639386 +0000 UTC
 
 package optional
 
@@ -56,11 +56,16 @@ func (s String) MarshalJSON() ([]byte, error) {
 	if s.Present() {
 		return json.Marshal(s.value)
 	}
-	var zero string
-	return json.Marshal(zero)
+	return json.Marshal(nil)
 }
 
 func (s *String) UnmarshalJSON(data []byte) error {
+
+	if string(data) == "null" {
+		s.value = nil
+		return nil
+	}
+
 	var value string
 
 	if err := json.Unmarshal(data, &value); err != nil {
diff --git a/complex128.go b/complex128.go
index e6954c3..b85dfbe 100644
--- a/complex128.go
+++ b/complex128.go
@@ -1,5 +1,5 @@
 // Code generated by go generate
-// This file was generated by robots at 2018-11-14 00:52:26.694747 +0000 UTC
+// This file was generated by robots at 2018-12-06 14:29:54.128811 +0000 UTC
 
 package optional
 
@@ -56,11 +56,16 @@ func (c Complex128) MarshalJSON() ([]byte, error) {
 	if c.Present() {
 		return json.Marshal(c.value)
 	}
-	var zero complex128
-	return json.Marshal(zero)
+	return json.Marshal(nil)
 }
 
 func (c *Complex128) UnmarshalJSON(data []byte) error {
+
+	if string(data) == "null" {
+		c.value = nil
+		return nil
+	}
+
 	var value complex128
 
 	if err := json.Unmarshal(data, &value); err != nil {
diff --git a/complex64.go b/complex64.go
index 4e011eb..04d5ee5 100644
--- a/complex64.go
+++ b/complex64.go
@@ -1,5 +1,5 @@
 // Code generated by go generate
-// This file was generated by robots at 2018-11-14 00:52:27.082956 +0000 UTC
+// This file was generated by robots at 2018-12-06 14:29:54.464548 +0000 UTC
 
 package optional
 
@@ -56,11 +56,16 @@ func (c Complex64) MarshalJSON() ([]byte, error) {
 	if c.Present() {
 		return json.Marshal(c.value)
 	}
-	var zero complex64
-	return json.Marshal(zero)
+	return json.Marshal(nil)
 }
 
 func (c *Complex64) UnmarshalJSON(data []byte) error {
+
+	if string(data) == "null" {
+		c.value = nil
+		return nil
+	}
+
 	var value complex64
 
 	if err := json.Unmarshal(data, &value); err != nil {
diff --git a/error.go b/error.go
index 41d3b7a..bc79ddc 100644
--- a/error.go
+++ b/error.go
@@ -1,5 +1,5 @@
 // Code generated by go generate
-// This file was generated by robots at 2018-11-14 00:52:27.535329 +0000 UTC
+// This file was generated by robots at 2018-12-06 14:29:54.804224 +0000 UTC
 
 package optional
 
@@ -56,11 +56,16 @@ func (e Error) MarshalJSON() ([]byte, error) {
 	if e.Present() {
 		return json.Marshal(e.value)
 	}
-	var zero error
-	return json.Marshal(zero)
+	return json.Marshal(nil)
 }
 
 func (e *Error) UnmarshalJSON(data []byte) error {
+
+	if string(data) == "null" {
+		e.value = nil
+		return nil
+	}
+
 	var value error
 
 	if err := json.Unmarshal(data, &value); err != nil {
diff --git a/float32.go b/float32.go
index eb78e2e..9f42c2c 100644
--- a/float32.go
+++ b/float32.go
@@ -1,5 +1,5 @@
 // Code generated by go generate
-// This file was generated by robots at 2018-11-14 00:52:27.939662 +0000 UTC
+// This file was generated by robots at 2018-12-06 14:29:55.1819 +0000 UTC
 
 package optional
 
@@ -56,11 +56,16 @@ func (f Float32) MarshalJSON() ([]byte, error) {
 	if f.Present() {
 		return json.Marshal(f.value)
 	}
-	var zero float32
-	return json.Marshal(zero)
+	return json.Marshal(nil)
 }
 
 func (f *Float32) UnmarshalJSON(data []byte) error {
+
+	if string(data) == "null" {
+		f.value = nil
+		return nil
+	}
+
 	var value float32
 
 	if err := json.Unmarshal(data, &value); err != nil {
diff --git a/float64.go b/float64.go
index 1125530..15966b6 100644
--- a/float64.go
+++ b/float64.go
@@ -1,5 +1,5 @@
 // Code generated by go generate
-// This file was generated by robots at 2018-11-14 00:52:28.345245 +0000 UTC
+// This file was generated by robots at 2018-12-06 14:29:55.521255 +0000 UTC
 
 package optional
 
@@ -56,11 +56,16 @@ func (f Float64) MarshalJSON() ([]byte, error) {
 	if f.Present() {
 		return json.Marshal(f.value)
 	}
-	var zero float64
-	return json.Marshal(zero)
+	return json.Marshal(nil)
 }
 
 func (f *Float64) UnmarshalJSON(data []byte) error {
+
+	if string(data) == "null" {
+		f.value = nil
+		return nil
+	}
+
 	var value float64
 
 	if err := json.Unmarshal(data, &value); err != nil {
diff --git a/int.go b/int.go
index f675e32..caead99 100644
--- a/int.go
+++ b/int.go
@@ -1,5 +1,5 @@
 // Code generated by go generate
-// This file was generated by robots at 2018-11-14 00:52:28.766753 +0000 UTC
+// This file was generated by robots at 2018-12-06 14:29:55.863991 +0000 UTC
 
 package optional
 
@@ -56,11 +56,16 @@ func (i Int) MarshalJSON() ([]byte, error) {
 	if i.Present() {
 		return json.Marshal(i.value)
 	}
-	var zero int
-	return json.Marshal(zero)
+	return json.Marshal(nil)
 }
 
 func (i *Int) UnmarshalJSON(data []byte) error {
+
+	if string(data) == "null" {
+		i.value = nil
+		return nil
+	}
+
 	var value int
 
 	if err := json.Unmarshal(data, &value); err != nil {
diff --git a/int16.go b/int16.go
index a6da247..9532996 100644
--- a/int16.go
+++ b/int16.go
@@ -1,5 +1,5 @@
 // Code generated by go generate
-// This file was generated by robots at 2018-11-14 00:52:29.175694 +0000 UTC
+// This file was generated by robots at 2018-12-06 14:29:56.212093 +0000 UTC
 
 package optional
 
@@ -56,11 +56,16 @@ func (i Int16) MarshalJSON() ([]byte, error) {
 	if i.Present() {
 		return json.Marshal(i.value)
 	}
-	var zero int16
-	return json.Marshal(zero)
+	return json.Marshal(nil)
 }
 
 func (i *Int16) UnmarshalJSON(data []byte) error {
+
+	if string(data) == "null" {
+		i.value = nil
+		return nil
+	}
+
 	var value int16
 
 	if err := json.Unmarshal(data, &value); err != nil {
diff --git a/int32.go b/int32.go
index f759790..07c212d 100644
--- a/int32.go
+++ b/int32.go
@@ -1,5 +1,5 @@
 // Code generated by go generate
-// This file was generated by robots at 2018-11-14 00:52:29.586464 +0000 UTC
+// This file was generated by robots at 2018-12-06 14:29:56.641482 +0000 UTC
 
 package optional
 
@@ -56,11 +56,16 @@ func (i Int32) MarshalJSON() ([]byte, error) {
 	if i.Present() {
 		return json.Marshal(i.value)
 	}
-	var zero int32
-	return json.Marshal(zero)
+	return json.Marshal(nil)
 }
 
 func (i *Int32) UnmarshalJSON(data []byte) error {
+
+	if string(data) == "null" {
+		i.value = nil
+		return nil
+	}
+
 	var value int32
 
 	if err := json.Unmarshal(data, &value); err != nil {
diff --git a/int64.go b/int64.go
index 0089cc3..7f8f01c 100644
--- a/int64.go
+++ b/int64.go
@@ -1,5 +1,5 @@
 // Code generated by go generate
-// This file was generated by robots at 2018-11-14 00:52:30.027992 +0000 UTC
+// This file was generated by robots at 2018-12-06 14:29:57.002648 +0000 UTC
 
 package optional
 
@@ -56,11 +56,16 @@ func (i Int64) MarshalJSON() ([]byte, error) {
 	if i.Present() {
 		return json.Marshal(i.value)
 	}
-	var zero int64
-	return json.Marshal(zero)
+	return json.Marshal(nil)
 }
 
 func (i *Int64) UnmarshalJSON(data []byte) error {
+
+	if string(data) == "null" {
+		i.value = nil
+		return nil
+	}
+
 	var value int64
 
 	if err := json.Unmarshal(data, &value); err != nil {
diff --git a/int8.go b/int8.go
index 4cdb349..182f814 100644
--- a/int8.go
+++ b/int8.go
@@ -1,5 +1,5 @@
 // Code generated by go generate
-// This file was generated by robots at 2018-11-14 00:52:30.427813 +0000 UTC
+// This file was generated by robots at 2018-12-06 14:29:57.555216 +0000 UTC
 
 package optional
 
@@ -56,11 +56,16 @@ func (i Int8) MarshalJSON() ([]byte, error) {
 	if i.Present() {
 		return json.Marshal(i.value)
 	}
-	var zero int8
-	return json.Marshal(zero)
+	return json.Marshal(nil)
 }
 
 func (i *Int8) UnmarshalJSON(data []byte) error {
+
+	if string(data) == "null" {
+		i.value = nil
+		return nil
+	}
+
 	var value int8
 
 	if err := json.Unmarshal(data, &value); err != nil {
diff --git a/rune.go b/rune.go
index a68653a..469de67 100644
--- a/rune.go
+++ b/rune.go
@@ -1,5 +1,5 @@
 // Code generated by go generate
-// This file was generated by robots at 2018-11-14 00:52:30.867604 +0000 UTC
+// This file was generated by robots at 2018-12-06 14:29:57.969673 +0000 UTC
 
 package optional
 
@@ -56,11 +56,16 @@ func (r Rune) MarshalJSON() ([]byte, error) {
 	if r.Present() {
 		return json.Marshal(r.value)
 	}
-	var zero rune
-	return json.Marshal(zero)
+	return json.Marshal(nil)
 }
 
 func (r *Rune) UnmarshalJSON(data []byte) error {
+
+	if string(data) == "null" {
+		r.value = nil
+		return nil
+	}
+
 	var value rune
 
 	if err := json.Unmarshal(data, &value); err != nil {
diff --git a/string.go b/string.go
index a346334..19e67c1 100644
--- a/string.go
+++ b/string.go
@@ -1,5 +1,5 @@
 // Code generated by go generate
-// This file was generated by robots at 2018-11-14 00:52:31.29776 +0000 UTC
+// This file was generated by robots at 2018-12-06 14:29:58.516631 +0000 UTC
 
 package optional
 
@@ -56,11 +56,16 @@ func (s String) MarshalJSON() ([]byte, error) {
 	if s.Present() {
 		return json.Marshal(s.value)
 	}
-	var zero string
-	return json.Marshal(zero)
+	return json.Marshal(nil)
 }
 
 func (s *String) UnmarshalJSON(data []byte) error {
+
+	if string(data) == "null" {
+		s.value = nil
+		return nil
+	}
+
 	var value string
 
 	if err := json.Unmarshal(data, &value); err != nil {
diff --git a/uint.go b/uint.go
index c9e610e..33e93e3 100644
--- a/uint.go
+++ b/uint.go
@@ -1,5 +1,5 @@
 // Code generated by go generate
-// This file was generated by robots at 2018-11-14 00:52:31.699785 +0000 UTC
+// This file was generated by robots at 2018-12-06 14:29:58.898667 +0000 UTC
 
 package optional
 
@@ -56,11 +56,16 @@ func (u Uint) MarshalJSON() ([]byte, error) {
 	if u.Present() {
 		return json.Marshal(u.value)
 	}
-	var zero uint
-	return json.Marshal(zero)
+	return json.Marshal(nil)
 }
 
 func (u *Uint) UnmarshalJSON(data []byte) error {
+
+	if string(data) == "null" {
+		u.value = nil
+		return nil
+	}
+
 	var value uint
 
 	if err := json.Unmarshal(data, &value); err != nil {
diff --git a/uint16.go b/uint16.go
index d7c7591..428ecbf 100644
--- a/uint16.go
+++ b/uint16.go
@@ -1,5 +1,5 @@
 // Code generated by go generate
-// This file was generated by robots at 2018-11-14 00:52:32.12056 +0000 UTC
+// This file was generated by robots at 2018-12-06 14:29:59.455534 +0000 UTC
 
 package optional
 
@@ -56,11 +56,16 @@ func (u Uint16) MarshalJSON() ([]byte, error) {
 	if u.Present() {
 		return json.Marshal(u.value)
 	}
-	var zero uint16
-	return json.Marshal(zero)
+	return json.Marshal(nil)
 }
 
 func (u *Uint16) UnmarshalJSON(data []byte) error {
+
+	if string(data) == "null" {
+		u.value = nil
+		return nil
+	}
+
 	var value uint16
 
 	if err := json.Unmarshal(data, &value); err != nil {
diff --git a/uint32.go b/uint32.go
index 125b416..5fa2ebf 100644
--- a/uint32.go
+++ b/uint32.go
@@ -1,5 +1,5 @@
 // Code generated by go generate
-// This file was generated by robots at 2018-11-14 00:52:32.56791 +0000 UTC
+// This file was generated by robots at 2018-12-06 14:29:59.856381 +0000 UTC
 
 package optional
 
@@ -56,11 +56,16 @@ func (u Uint32) MarshalJSON() ([]byte, error) {
 	if u.Present() {
 		return json.Marshal(u.value)
 	}
-	var zero uint32
-	return json.Marshal(zero)
+	return json.Marshal(nil)
 }
 
 func (u *Uint32) UnmarshalJSON(data []byte) error {
+
+	if string(data) == "null" {
+		u.value = nil
+		return nil
+	}
+
 	var value uint32
 
 	if err := json.Unmarshal(data, &value); err != nil {
diff --git a/uint64.go b/uint64.go
index 1252c06..f0d79a4 100644
--- a/uint64.go
+++ b/uint64.go
@@ -1,5 +1,5 @@
 // Code generated by go generate
-// This file was generated by robots at 2018-11-14 00:52:32.98085 +0000 UTC
+// This file was generated by robots at 2018-12-06 14:30:00.317311 +0000 UTC
 
 package optional
 
@@ -56,11 +56,16 @@ func (u Uint64) MarshalJSON() ([]byte, error) {
 	if u.Present() {
 		return json.Marshal(u.value)
 	}
-	var zero uint64
-	return json.Marshal(zero)
+	return json.Marshal(nil)
 }
 
 func (u *Uint64) UnmarshalJSON(data []byte) error {
+
+	if string(data) == "null" {
+		u.value = nil
+		return nil
+	}
+
 	var value uint64
 
 	if err := json.Unmarshal(data, &value); err != nil {
diff --git a/uint8.go b/uint8.go
index 920cb84..9b2be7f 100644
--- a/uint8.go
+++ b/uint8.go
@@ -1,5 +1,5 @@
 // Code generated by go generate
-// This file was generated by robots at 2018-11-14 00:52:33.373985 +0000 UTC
+// This file was generated by robots at 2018-12-06 14:30:00.699077 +0000 UTC
 
 package optional
 
@@ -56,11 +56,16 @@ func (u Uint8) MarshalJSON() ([]byte, error) {
 	if u.Present() {
 		return json.Marshal(u.value)
 	}
-	var zero uint8
-	return json.Marshal(zero)
+	return json.Marshal(nil)
 }
 
 func (u *Uint8) UnmarshalJSON(data []byte) error {
+
+	if string(data) == "null" {
+		u.value = nil
+		return nil
+	}
+
 	var value uint8
 
 	if err := json.Unmarshal(data, &value); err != nil {
diff --git a/uintptr.go b/uintptr.go
index b947661..af79fef 100644
--- a/uintptr.go
+++ b/uintptr.go
@@ -1,5 +1,5 @@
 // Code generated by go generate
-// This file was generated by robots at 2018-11-14 00:52:33.811844 +0000 UTC
+// This file was generated by robots at 2018-12-06 14:30:01.109101 +0000 UTC
 
 package optional
 
@@ -56,11 +56,16 @@ func (u Uintptr) MarshalJSON() ([]byte, error) {
 	if u.Present() {
 		return json.Marshal(u.value)
 	}
-	var zero uintptr
-	return json.Marshal(zero)
+	return json.Marshal(nil)
 }
 
 func (u *Uintptr) UnmarshalJSON(data []byte) error {
+
+	if string(data) == "null" {
+		u.value = nil
+		return nil
+	}
+
 	var value uintptr
 
 	if err := json.Unmarshal(data, &value); err != nil {