diff --git a/packages/frontend-internal/src/wiring/OpaqueType.test.ts b/packages/frontend-internal/src/wiring/OpaqueType.test.ts
index 10ca93bfa8..edf23cd732 100644
--- a/packages/frontend-internal/src/wiring/OpaqueType.test.ts
+++ b/packages/frontend-internal/src/wiring/OpaqueType.test.ts
@@ -131,17 +131,17 @@ describe('OpaqueType', () => {
     expect(() =>
       OpaqueMyType.toInternal({ $$type: 'my-type' }),
     ).toThrowErrorMatchingInlineSnapshot(
-      `"Invalid opaque type instance, got version 'undefined', expected one of ['v1']"`,
+      `"Invalid opaque type instance, got version undefined, expected 'v1'"`,
     );
     expect(() =>
-      OpaqueMyType.toInternal({ $$type: 'my-type', version: 'v3' }),
+      OpaqueMyType.toInternal({ $$type: 'my-type', version: 'v0' }),
     ).toThrowErrorMatchingInlineSnapshot(
-      `"Invalid opaque type instance, got version 'v3', expected one of ['v1']"`,
+      `"Invalid opaque type instance, got version 'v0', expected 'v1'"`,
     );
     expect(() =>
       OpaqueMyType.toInternal({ $$type: 'my-type', version: { foo: 'bar' } }),
     ).toThrowErrorMatchingInlineSnapshot(
-      `"Invalid opaque type instance, got version '[object Object]', expected one of ['v1']"`,
+      `"Invalid opaque type instance, got version '[object Object]', expected 'v1'"`,
     );
   });
 
@@ -160,10 +160,14 @@ describe('OpaqueType', () => {
         | {
             version: 'v2';
             bar: string;
+          }
+        | {
+            version: 'v3';
+            baz: string;
           };
     }>({
       type: 'my-type',
-      versions: ['v1', 'v2'],
+      versions: ['v1', 'v2', 'v3'],
     });
 
     OpaqueMyType.create({
@@ -176,7 +180,7 @@ describe('OpaqueType', () => {
     OpaqueMyType.create({
       $$type: 'my-type',
       // @ts-expect-error - unsupported version
-      version: 'v3',
+      version: 'v0',
       foo: 'bar',
     });
 
@@ -264,12 +268,12 @@ describe('OpaqueType', () => {
     expect(() =>
       OpaqueMyType.toInternal({ $$type: 'my-type' }),
     ).toThrowErrorMatchingInlineSnapshot(
-      `"Invalid opaque type instance, got version 'undefined', expected one of ['v1', 'v2']"`,
+      `"Invalid opaque type instance, got version undefined, expected 'v1', 'v2', or 'v3'"`,
     );
     expect(() =>
-      OpaqueMyType.toInternal({ $$type: 'my-type', version: 'v3' }),
+      OpaqueMyType.toInternal({ $$type: 'my-type', version: 'v0' }),
     ).toThrowErrorMatchingInlineSnapshot(
-      `"Invalid opaque type instance, got version 'v3', expected one of ['v1', 'v2']"`,
+      `"Invalid opaque type instance, got version 'v0', expected 'v1', 'v2', or 'v3'"`,
     );
   });
 
@@ -339,9 +343,9 @@ describe('OpaqueType', () => {
 
     expect(OpaqueMyType.toInternal({ $$type: 'my-type' })).toBeDefined();
     expect(() =>
-      OpaqueMyType.toInternal({ $$type: 'my-type', version: 'v3' }),
+      OpaqueMyType.toInternal({ $$type: 'my-type', version: 'v0' }),
     ).toThrowErrorMatchingInlineSnapshot(
-      `"Invalid opaque type instance, got version 'v3', expected undefined"`,
+      `"Invalid opaque type instance, got version 'v0', expected undefined"`,
     );
   });
 
@@ -363,7 +367,7 @@ describe('OpaqueType', () => {
           };
     }>({
       type: 'my-type',
-      versions: ['v1', undefined],
+      versions: [undefined, 'v1'],
     });
 
     OpaqueMyType.create({
@@ -465,7 +469,7 @@ describe('OpaqueType', () => {
     expect(() =>
       OpaqueMyType.toInternal({ $$type: 'my-type', version: 'v3' }),
     ).toThrowErrorMatchingInlineSnapshot(
-      `"Invalid opaque type instance, got version 'v3', expected undefined or one of ['v1']"`,
+      `"Invalid opaque type instance, got version 'v3', expected undefined or 'v1'"`,
     );
   });
 });
diff --git a/packages/frontend-internal/src/wiring/OpaqueType.ts b/packages/frontend-internal/src/wiring/OpaqueType.ts
index 5da3003418..5a13529388 100644
--- a/packages/frontend-internal/src/wiring/OpaqueType.ts
+++ b/packages/frontend-internal/src/wiring/OpaqueType.ts
@@ -99,18 +99,16 @@ export class OpaqueType<
     }
 
     if (!this.#versions.has(value.version)) {
-      const expected = [];
-      if (this.#versions.has(undefined)) {
-        expected.push('undefined');
-      }
-      const versions = Array.from(this.#versions).filter(Boolean);
-      if (versions.length > 0) {
-        expected.push(`one of ['${versions.join("', '")}']`);
+      const versions = Array.from(this.#versions).map(this.#stringifyVersion);
+      if (versions.length > 1) {
+        versions[versions.length - 1] = `or ${versions[versions.length - 1]}`;
       }
+      const expected =
+        versions.length > 2 ? versions.join(', ') : versions.join(' ');
       throw new TypeError(
-        `Invalid opaque type instance, got version '${
-          value.version
-        }', expected ${expected.join(' or ')}`,
+        `Invalid opaque type instance, got version ${this.#stringifyVersion(
+          value.version,
+        )}, expected ${expected}`,
       );
     }
 
@@ -147,4 +145,8 @@ export class OpaqueType<
     }
     return String(value);
   }
+
+  #stringifyVersion = (version: string | undefined) => {
+    return version ? `'${version}'` : 'undefined';
+  };
 }