diff --git a/src/eth/erc4337/types.test.ts b/src/eth/erc4337/types.test.ts
index 50175e498..b7c065d76 100644
--- a/src/eth/erc4337/types.test.ts
+++ b/src/eth/erc4337/types.test.ts
@@ -1,6 +1,6 @@
 import { assert } from 'superstruct';
 
-import { EthUserOperationStruct } from './types';
+import { EthUserOperationStruct, EthBaseUserOperationStruct } from './types';
 
 describe('types', () => {
   it('is a valid UserOperation', () => {
@@ -76,4 +76,59 @@ describe('types', () => {
       'At path: nonce -- Expected a value of type `EthUint256`, but received: `"0x01"`',
     );
   });
+
+  describe('EthBaseUserOperationStruct', () => {
+    const baseUserOp = {
+      nonce: '0x1',
+      initCode: '0x',
+      callData: '0x70641a22000000000000000000000000',
+      gasLimits: {
+        callGasLimit: '0x58a83',
+        verificationGasLimit: '0xe8c4',
+        preVerificationGas: '0xc57c',
+      },
+      dummyPaymasterAndData: '0x1234',
+      dummySignature: '0x1234',
+    };
+
+    it('is a valid BaseUserOperation', () => {
+      const userOp = {
+        ...baseUserOp,
+        bundlerUrl: 'https://example.com',
+      };
+      expect(() => assert(userOp, EthBaseUserOperationStruct)).not.toThrow();
+    });
+
+    it('has an invalid BaseUserOperation with an incorrect url string', () => {
+      const userOp = {
+        ...baseUserOp,
+        bundlerUrl: 'random string',
+      };
+      expect(() => assert(userOp, EthBaseUserOperationStruct)).toThrow(
+        'At path: bundlerUrl -- Expected a value of type `Url`, but received: `"random string"`',
+      );
+    });
+
+    it('cannot have an empty bundler url', () => {
+      const userOp = {
+        ...baseUserOp,
+        bundlerUrl: '',
+      };
+      expect(() => assert(userOp, EthBaseUserOperationStruct)).toThrow(
+        'At path: bundlerUrl -- Expected a value of type `Url`, but received: `""`',
+      );
+    });
+
+    it('does not throw if gasLimits are undefined', () => {
+      const userOp = {
+        nonce: '0x1',
+        initCode: '0x',
+        callData: '0x70641a22000000000000000000000000',
+        dummyPaymasterAndData: '0x1234',
+        dummySignature: '0x1234',
+        bundlerUrl: 'https://example.com',
+      };
+      expect(() => assert(userOp, EthBaseUserOperationStruct)).not.toThrow();
+    });
+  });
 });
diff --git a/src/eth/erc4337/types.ts b/src/eth/erc4337/types.ts
index 75afdc037..b1376ac67 100644
--- a/src/eth/erc4337/types.ts
+++ b/src/eth/erc4337/types.ts
@@ -1,6 +1,6 @@
-import { string, type Infer } from 'superstruct';
+import { type Infer } from 'superstruct';
 
-import { exactOptional, object } from '../../superstruct';
+import { UrlStruct, exactOptional, object } from '../../superstruct';
 import { EthAddressStruct, EthBytesStruct, EthUint256Struct } from '../types';
 
 /**
@@ -59,7 +59,7 @@ export const EthBaseUserOperationStruct = object({
   ),
   dummyPaymasterAndData: EthBytesStruct,
   dummySignature: EthBytesStruct,
-  bundlerUrl: string(),
+  bundlerUrl: UrlStruct,
 });
 
 export type EthBaseUserOperation = Infer<typeof EthBaseUserOperationStruct>;
diff --git a/src/eth/types.test.ts b/src/eth/types.test.ts
new file mode 100644
index 000000000..7a6c74846
--- /dev/null
+++ b/src/eth/types.test.ts
@@ -0,0 +1,30 @@
+import { UrlStruct } from '../superstruct';
+
+describe('types', () => {
+  it('is a valid BundlerUrl', () => {
+    const url = 'https://api.example.com';
+    expect(() => UrlStruct.assert(url)).not.toThrow();
+  });
+
+  it('is a valid BundlerUrl with query parameters', () => {
+    const url = 'https://api.example.com?foo=bar';
+    expect(() => UrlStruct.assert(url)).not.toThrow();
+  });
+
+  it('accepts path parameters', () => {
+    const url = 'https://api.example.com/foo/bar';
+    expect(() => UrlStruct.assert(url)).not.toThrow();
+  });
+
+  it('fails if it does not start with http or https', () => {
+    const url = 'ftp://api.example.com';
+    expect(() => UrlStruct.assert(url)).toThrow(
+      'Expected a value of type `Url`, but received: `"ftp://api.example.com"`',
+    );
+  });
+
+  it('has to start with http or https', () => {
+    const url = 'http://api.example.com';
+    expect(() => UrlStruct.assert(url)).not.toThrow();
+  });
+});
diff --git a/src/superstruct.ts b/src/superstruct.ts
index a3c6e0c1f..0bb8e6568 100644
--- a/src/superstruct.ts
+++ b/src/superstruct.ts
@@ -125,3 +125,21 @@ export function definePattern(
       typeof value === 'string' && pattern.test(value),
   );
 }
+
+/**
+ * Validates if a given value is a valid URL.
+ *
+ * @param value - The value to be validated.
+ * @returns A boolean indicating if the value is a valid URL.
+ */
+export const UrlStruct = define('Url', (value: unknown) => {
+  let url;
+
+  try {
+    url = new URL(value as string);
+  } catch (_) {
+    return false;
+  }
+
+  return url.protocol === 'http:' || url.protocol === 'https:';
+});