diff --git a/packages/functions-tools/src/converters/zod-to-rust.ts b/packages/functions-tools/src/converters/zod-to-rust.ts
index f57f7215a..f553db419 100644
--- a/packages/functions-tools/src/converters/zod-to-rust.ts
+++ b/packages/functions-tools/src/converters/zod-to-rust.ts
@@ -103,7 +103,7 @@ const schemaToRustType = ({
       const inner = schemaToRustType({schema: schema.inner, structName});
       const fieldType = `Option<${inner.fieldType}>`;
       return inner.kind === 'composite'
-        ? composite({fieldType, structs: inner.structs})
+        ? composite({fieldType, structs: inner.structs, needsJsonData: inner.needsJsonData})
         : primitive({fieldType});
     }
 
diff --git a/packages/functions-tools/src/tests/converters/zod-to-rust.spec.ts b/packages/functions-tools/src/tests/converters/zod-to-rust.spec.ts
index f30e22bc7..a5cb1a0ef 100644
--- a/packages/functions-tools/src/tests/converters/zod-to-rust.spec.ts
+++ b/packages/functions-tools/src/tests/converters/zod-to-rust.spec.ts
@@ -87,6 +87,15 @@ describe('object with enum field', () => {
       '#[derive(CandidType, Serialize, Deserialize, Clone, JsonData)]\npub struct MyFunctionArgs {\n    pub status: MyFunctionArgsStatus,\n}'
     ].join('\n\n')
   );
+
+  rust(
+    'myFunction',
+    z.object({role: z.enum(['admin', 'user']).optional()}),
+    [
+      '#[derive(CandidType, Serialize, Deserialize, Clone)]\npub enum MyFunctionArgsRole {\n    #[serde(rename = "admin")]\n    Admin,\n    #[serde(rename = "user")]\n    User,\n}',
+      '#[derive(CandidType, Serialize, Deserialize, Clone, JsonData)]\npub struct MyFunctionArgs {\n    pub role: Option<MyFunctionArgsRole>,\n}'
+    ].join('\n\n')
+  );
 });
 
 // ─── Arrays ───────────────────────────────────────────────────────────────────