diff --git a/codecs/test/__snapshots__/object.test.ts.snap b/codecs/test/__snapshots__/object.test.ts.snap
index de39e02..cd65e37 100644
--- a/codecs/test/__snapshots__/object.test.ts.snap
+++ b/codecs/test/__snapshots__/object.test.ts.snap
@@ -71,7 +71,10 @@ snapshot[`\$person invalid { name: "", nickName: "", superPower: "", unluckyNumb
 snapshot[`\$.object(
   \$.taggedUnion(
     "_tag",
-    [ { tag: "a", codec: \$.object(Array) }, { tag: "b", codec: \$.object(Array) } ]
+    [
+      Variant { tag: "a", codec: \$.object(Array) },
+      Variant { tag: "b", codec: \$.object(Array) }
+    ]
   ),
   \$.field("bar", \$.u8)
 ) { _tag: "a", bar: 123 } 1`] = `
@@ -82,7 +85,10 @@ snapshot[`\$.object(
 snapshot[`\$.object(
   \$.taggedUnion(
     "_tag",
-    [ { tag: "a", codec: \$.object(Array) }, { tag: "b", codec: \$.object(Array) } ]
+    [
+      Variant { tag: "a", codec: \$.object(Array) },
+      Variant { tag: "b", codec: \$.object(Array) }
+    ]
   ),
   \$.field("bar", \$.u8)
 ) { _tag: "b", x: 0, bar: 123 } 1`] = `
@@ -94,7 +100,10 @@ snapshot[`\$.object(
 snapshot[`\$.object(
   \$.taggedUnion(
     "_tag",
-    [ { tag: "a", codec: \$.object(Array) }, { tag: "b", codec: \$.object(Array) } ]
+    [
+      Variant { tag: "a", codec: \$.object(Array) },
+      Variant { tag: "b", codec: \$.object(Array) }
+    ]
   ),
   \$.field("bar", \$.u8)
 ) invalid null 1`] = `ScaleAssertError: value == null`;
@@ -102,7 +111,10 @@ snapshot[`\$.object(
 snapshot[`\$.object(
   \$.taggedUnion(
     "_tag",
-    [ { tag: "a", codec: \$.object(Array) }, { tag: "b", codec: \$.object(Array) } ]
+    [
+      Variant { tag: "a", codec: \$.object(Array) },
+      Variant { tag: "b", codec: \$.object(Array) }
+    ]
   ),
   \$.field("bar", \$.u8)
 ) invalid { _tag: null, bar: 1 } 1`] = `ScaleAssertError: typeof value._tag !== "string"`;
@@ -110,7 +122,10 @@ snapshot[`\$.object(
 snapshot[`\$.object(
   \$.taggedUnion(
     "_tag",
-    [ { tag: "a", codec: \$.object(Array) }, { tag: "b", codec: \$.object(Array) } ]
+    [
+      Variant { tag: "a", codec: \$.object(Array) },
+      Variant { tag: "b", codec: \$.object(Array) }
+    ]
   ),
   \$.field("bar", \$.u8)
 ) invalid { _tag: "", bar: 1 } 1`] = `ScaleAssertError: value._tag: invalid tag`;
@@ -118,7 +133,10 @@ snapshot[`\$.object(
 snapshot[`\$.object(
   \$.taggedUnion(
     "_tag",
-    [ { tag: "a", codec: \$.object(Array) }, { tag: "b", codec: \$.object(Array) } ]
+    [
+      Variant { tag: "a", codec: \$.object(Array) },
+      Variant { tag: "b", codec: \$.object(Array) }
+    ]
   ),
   \$.field("bar", \$.u8)
 ) invalid { _tag: "b", bar: 1 } 1`] = `ScaleAssertError: !("x" in value)`;
@@ -126,7 +144,10 @@ snapshot[`\$.object(
 snapshot[`\$.object(
   \$.taggedUnion(
     "_tag",
-    [ { tag: "a", codec: \$.object(Array) }, { tag: "b", codec: \$.object(Array) } ]
+    [
+      Variant { tag: "a", codec: \$.object(Array) },
+      Variant { tag: "b", codec: \$.object(Array) }
+    ]
   ),
   \$.field("bar", \$.u8)
 ) invalid { _tag: "b", x: -1, bar: 1 } 1`] = `ScaleAssertError: value.x < 0`;
@@ -134,7 +155,10 @@ snapshot[`\$.object(
 snapshot[`\$.object(
   \$.taggedUnion(
     "_tag",
-    [ { tag: "a", codec: \$.object(Array) }, { tag: "b", codec: \$.object(Array) } ]
+    [
+      Variant { tag: "a", codec: \$.object(Array) },
+      Variant { tag: "b", codec: \$.object(Array) }
+    ]
   ),
   \$.field("bar", \$.u8)
 ) invalid { _tag: "a", bar: -1 } 1`] = `ScaleAssertError: value.bar < 0`;
diff --git a/codecs/union.ts b/codecs/union.ts
index 12bc080..58e0b77 100644
--- a/codecs/union.ts
+++ b/codecs/union.ts
@@ -3,16 +3,15 @@ import { Codec, createCodec, Expand, metadata, Narrow, ScaleAssertError, ScaleDe
 import { constant } from "./constant.ts"
 import { field, NativeObject, object, ObjectMembers } from "./object.ts"
 
-export interface Variant<T extends string, V> {
-  tag: T
-  codec: Codec<V>
+export class Variant<T extends string, V> {
+  constructor(readonly tag: T, readonly codec: Codec<V>) {}
 }
 
 export function variant<T extends string, E extends AnyCodec[]>(
   tag: T,
   ...members: ObjectMembers<E>
 ): Variant<T, NativeObject<E>> {
-  return { tag, codec: object(...members) }
+  return new Variant(tag, object(...members))
 }
 
 export type NativeTaggedUnion<
diff --git a/common/codec.ts b/common/codec.ts
index 2fdce82..e7973ea 100644
--- a/common/codec.ts
+++ b/common/codec.ts
@@ -3,7 +3,6 @@ import { DecodeBuffer, EncodeBuffer } from "./buffer.ts"
 import { Metadata } from "./metadata.ts"
 import { ScaleAssertError, ScaleEncodeError } from "./util.ts"
 
-export type AnyCodec = Codec<any> | Codec<never>
 export type Native<T extends AnyCodec> = T extends Codec<infer U> ? U : never
 
 export function createCodec<T>(
@@ -39,39 +38,8 @@ const codecInspectCtx = new Map<Codec<any>, number | null>()
 let codecInspectIdN = 0
 const nodeCustomInspect = Symbol.for("nodejs.util.inspect.custom")
 const denoCustomInspect = Symbol.for("Deno.customInspect")
-export abstract class Codec<T> {
-  /** A static estimation of the size, which may be an under- or over-estimate */
-  abstract _staticSize: number
-  /** Encodes the value into the supplied buffer, which should have at least `_staticSize` free byte. */
-  abstract _encode: (buffer: EncodeBuffer, value: T) => void
-  /** Decodes the value from the supplied buffer */
-  abstract _decode: (buffer: DecodeBuffer) => T
-  /** Asserts that the value is valid for this codec */
-  abstract _assert: (state: AssertState) => void
-  /** An array with metadata representing the construction of this codec */
-  abstract _metadata: Metadata<T>
-
-  /** Encodes the value into a new Uint8Array (throws if async) */
-  encode(value: T) {
-    const buf = new EncodeBuffer(this._staticSize)
-    this._encode(buf, value)
-    if (buf.asyncCount) throw new ScaleEncodeError(this, value, "Attempted to synchronously encode an async codec")
-    return buf.finish()
-  }
-
-  /** Asynchronously encodes the value into a new Uint8Array */
-  async encodeAsync(value: T) {
-    const buf = new EncodeBuffer(this._staticSize)
-    this._encode(buf, value)
-    return buf.finishAsync()
-  }
-
-  /** Decodes a value from the supplied Uint8Array */
-  decode(array: Uint8Array) {
-    const buf = new DecodeBuffer(array)
-    return this._decode(buf)
-  }
 
+abstract class _Codec {
   private [nodeCustomInspect](_0: unknown, _1: unknown, inspect: (value: unknown) => string) {
     return this._inspect(inspect)
   }
@@ -82,7 +50,7 @@ export abstract class Codec<T> {
 
   // Properly handles circular codecs in the case of $.deferred
   private _inspect(inspect: (value: unknown) => string): string
-  private _inspect(this: Codec<T>, inspect: (value: unknown) => string): string {
+  private _inspect<T>(this: Codec<T>, inspect: (value: unknown) => string): string {
     let id = codecInspectCtx.get(this)
     if (id !== undefined) {
       if (id === null) {
@@ -115,6 +83,52 @@ export abstract class Codec<T> {
   }
 }
 
+export interface AnyCodec extends _Codec {
+  _staticSize: number
+  _encode(buffer: EncodeBuffer, value: any): void
+  _decode: (buffer: DecodeBuffer) => any
+  _assert: (state: AssertState) => void
+  _metadata: any
+
+  encode(value: any): Uint8Array
+  encodeAsync(value: any): Promise<Uint8Array>
+  decode(array: Uint8Array): any
+}
+
+export abstract class Codec<in out T> extends _Codec implements AnyCodec {
+  /** A static estimation of the size, which may be an under- or over-estimate */
+  abstract _staticSize: number
+  /** Encodes the value into the supplied buffer, which should have at least `_staticSize` free byte. */
+  abstract _encode: (buffer: EncodeBuffer, value: T) => void
+  /** Decodes the value from the supplied buffer */
+  abstract _decode: (buffer: DecodeBuffer) => T
+  /** Asserts that the value is valid for this codec */
+  abstract _assert: (state: AssertState) => void
+  /** An array with metadata representing the construction of this codec */
+  abstract _metadata: Metadata<T>
+
+  /** Encodes the value into a new Uint8Array (throws if async) */
+  encode(value: T) {
+    const buf = new EncodeBuffer(this._staticSize)
+    this._encode(buf, value)
+    if (buf.asyncCount) throw new ScaleEncodeError(this, value, "Attempted to synchronously encode an async codec")
+    return buf.finish()
+  }
+
+  /** Asynchronously encodes the value into a new Uint8Array */
+  async encodeAsync(value: T) {
+    const buf = new EncodeBuffer(this._staticSize)
+    this._encode(buf, value)
+    return buf.finishAsync()
+  }
+
+  /** Decodes a value from the supplied Uint8Array */
+  decode(array: Uint8Array) {
+    const buf = new DecodeBuffer(array)
+    return this._decode(buf)
+  }
+}
+
 export function assert<T>(codec: Codec<T>, value: unknown): asserts value is T {
   codec._assert(new AssertState(value))
 }