diff --git a/src/server/routes/backend-wallet/sign-typed-data.ts b/src/server/routes/backend-wallet/sign-typed-data.ts
index 6d0288b0..42eeb652 100644
--- a/src/server/routes/backend-wallet/sign-typed-data.ts
+++ b/src/server/routes/backend-wallet/sign-typed-data.ts
@@ -1,4 +1,5 @@
 import { type Static, Type } from "@sinclair/typebox";
+import { ethers } from "ethers";
 import type { FastifyInstance } from "fastify";
 import { StatusCodes } from "http-status-codes";
 import { arbitrumSepolia } from "thirdweb/chains";
@@ -60,6 +61,15 @@ export async function signTypedData(fastify: FastifyInstance) {
 
       const chain = chainId ? await getChain(chainId) : arbitrumSepolia;
 
+      let parsedPrimaryType = primaryType;
+      if (!parsedPrimaryType) {
+        // try to detect the primary type, which requires removing the EIP712Domain type
+        // biome-ignore lint/performance/noDelete: need to delete explicitely
+        delete (types as unknown as Record<string, unknown>).EIP712Domain;
+        parsedPrimaryType =
+          ethers.utils._TypedDataEncoder.getPrimaryType(types);
+      }
+
       const { account } = await walletDetailsToAccount({
         walletDetails,
         chain,
@@ -68,7 +78,7 @@ export async function signTypedData(fastify: FastifyInstance) {
       const result = await account.signTypedData({
         domain,
         types,
-        primaryType,
+        primaryType: parsedPrimaryType,
         message: value,
       } as never);
 
diff --git a/tests/e2e/tests/routes/sign-typed-data.test.ts b/tests/e2e/tests/routes/sign-typed-data.test.ts
new file mode 100644
index 00000000..f6b40179
--- /dev/null
+++ b/tests/e2e/tests/routes/sign-typed-data.test.ts
@@ -0,0 +1,78 @@
+import { describe, expect, test } from "bun:test";
+import { signTypedData } from "thirdweb/utils";
+import { ANVIL_PKEY_A } from "../../utils/wallets";
+import { setup } from "../setup";
+
+describe("signTypedDataRoute", () => {
+	const data = {
+		domain: {
+			name: "Ether Mail",
+			version: "1",
+			chainId: 1,
+			verifyingContract: "0x0000000000000000000000000000000000000000",
+		},
+		message: {
+			contents: "Hello, Bob!",
+			from: {
+				name: "Alice",
+			},
+		},
+		primaryType: "Mail",
+		types: {
+			EIP712Domain: [
+				{ name: "name", type: "string" },
+				{ name: "version", type: "string" },
+				{ name: "chainId", type: "uint256" },
+				{ name: "verifyingContract", type: "address" },
+			],
+			Mail: [
+				{ name: "contents", type: "string" },
+				{ name: "from", type: "Person" },
+			],
+			Person: [{ name: "name", type: "string" }],
+		},
+	} as const;
+
+	test("Sign typed data", async () => {
+		const { engine, backendWallet } = await setup();
+
+		const res = await engine.backendWallet.signTypedData(backendWallet, {
+			domain: data.domain,
+			value: data.message,
+			types: data.types,
+			primaryType: data.primaryType,
+		});
+
+		const expected = signTypedData({
+			// @ts-expect-error - bigint serialization
+			domain: data.domain,
+			message: data.message,
+			types: data.types,
+			primaryType: data.primaryType,
+			privateKey: ANVIL_PKEY_A,
+		});
+
+		expect(res.result).toEqual(expected);
+	});
+
+	test("Sign typed data without primary type", async () => {
+		const { engine, backendWallet } = await setup();
+
+		const res = await engine.backendWallet.signTypedData(backendWallet, {
+			domain: data.domain,
+			value: data.message,
+			types: data.types,
+		});
+
+		const expected = signTypedData({
+			// @ts-expect-error - bigint serialization
+			domain: data.domain,
+			message: data.message,
+			types: data.types,
+			primaryType: data.primaryType,
+			privateKey: ANVIL_PKEY_A,
+		});
+
+		expect(res.result).toEqual(expected);
+	});
+});