3 files changed, 74 insertions, 32 deletions
diff --git a/types/opt/value.go b/types/opt/value.go
index b47b03c81..bd90b5d90 100644
--- a/types/opt/value.go
+++ b/types/opt/value.go
@@ -6,9 +6,6 @@ package opt
 import (
 	"fmt"
 	"reflect"
-
-	jsonv2 "github.com/go-json-experiment/json"
-	"github.com/go-json-experiment/json/jsontext"
 )
 
 // Value is an optional value to be JSON-encoded.
@@ -99,32 +96,3 @@ func (o Value[T]) Equal(v Value[T]) bool {
 	}
 	return false
 }
-
-// MarshalJSONV2 implements [jsonv2.MarshalerV2].
-func (o Value[T]) MarshalJSONV2(enc *jsontext.Encoder, opts jsonv2.Options) error {
-	if !o.set {
-		return enc.WriteToken(jsontext.Null)
-	}
-	return jsonv2.MarshalEncode(enc, &o.value, opts)
-}
-
-// UnmarshalJSONV2 implements [jsonv2.UnmarshalerV2].
-func (o *Value[T]) UnmarshalJSONV2(dec *jsontext.Decoder, opts jsonv2.Options) error {
-	if dec.PeekKind() == 'n' {
-		*o = Value[T]{}
-		_, err := dec.ReadToken() // read null
-		return err
-	}
-	o.set = true
-	return jsonv2.UnmarshalDecode(dec, &o.value, opts)
-}
-
-// MarshalJSON implements [json.Marshaler].
-func (o Value[T]) MarshalJSON() ([]byte, error) {
-	return jsonv2.Marshal(o) // uses MarshalJSONV2
-}
-
-// UnmarshalJSON implements [json.Unmarshaler].
-func (o *Value[T]) UnmarshalJSON(b []byte) error {
-	return jsonv2.Unmarshal(b, o) // uses UnmarshalJSONV2
-}
diff --git a/types/opt/value_jsonv1.go b/types/opt/value_jsonv1.go
new file mode 100644
index 000000000..886d82468
--- /dev/null
+++ b/types/opt/value_jsonv1.go
@@ -0,0 +1,34 @@
+//go:build ts_omit_jsonv2
+
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+package value
+
+import (
+	"bytes"
+	"encoding/json"
+	"fmt"
+)
+
+var null = []byte("null")
+
+// MarshalJSON implements [json.Marshaler].
+func (o Value[T]) MarshalJSON() ([]byte, error) {
+	if !o.set {
+		return null, nil
+	}
+	return json.Marshal(o.value)
+}
+
+// UnmarshalJSON implements [json.Unmarshaler].
+func (o *Value[T]) UnmarshalJSON(b []byte) error {
+	if len(b) > 0 && b[0] == 'n' {
+		*o = Value[T]{}
+		if !bytes.Equal(b, null) {
+			return fmt.Errorf("invalid literal %q, expected %q", b, null)
+		}
+		return nil
+	}
+	return json.Unmarshal(&o.value, b)
+}
diff --git a/types/opt/value_jsonv2.go b/types/opt/value_jsonv2.go
new file mode 100644
index 000000000..e2e35865e
--- /dev/null
+++ b/types/opt/value_jsonv2.go
@@ -0,0 +1,40 @@
+//go:build !ts_omit_jsonv2
+
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+package opt
+
+import (
+	jsonv2 "github.com/go-json-experiment/json"
+	"github.com/go-json-experiment/json/jsontext"
+)
+
+// MarshalJSON implements [json.Marshaler].
+func (o Value[T]) MarshalJSON() ([]byte, error) {
+	return jsonv2.Marshal(o) // uses MarshalJSONV2
+}
+
+// UnmarshalJSON implements [json.Unmarshaler].
+func (o *Value[T]) UnmarshalJSON(b []byte) error {
+	return jsonv2.Unmarshal(b, o) // uses UnmarshalJSONV2
+}
+
+// MarshalJSONV2 implements [jsonv2.MarshalerV2].
+func (o Value[T]) MarshalJSONV2(enc *jsontext.Encoder, opts jsonv2.Options) error {
+	if !o.set {
+		return enc.WriteToken(jsontext.Null)
+	}
+	return jsonv2.MarshalEncode(enc, &o.value, opts)
+}
+
+// UnmarshalJSONV2 implements [jsonv2.UnmarshalerV2].
+func (o *Value[T]) UnmarshalJSONV2(dec *jsontext.Decoder, opts jsonv2.Options) error {
+	if dec.PeekKind() == 'n' {
+		*o = Value[T]{}
+		_, err := dec.ReadToken() // read null
+		return err
+	}
+	o.set = true
+	return jsonv2.UnmarshalDecode(dec, &o.value, opts)
+}