diff --git a/packages/abi-gen-wrappers/src/generated-wrappers/i_validator.ts b/packages/abi-gen-wrappers/src/generated-wrappers/i_validator.ts
index 86dae30e10..b7ae7dc8a7 100644
--- a/packages/abi-gen-wrappers/src/generated-wrappers/i_validator.ts
+++ b/packages/abi-gen-wrappers/src/generated-wrappers/i_validator.ts
@@ -38,7 +38,7 @@ export class IValidatorContract extends BaseContract {
          * @param hash Message hash that is signed.
          * @param signerAddress Address that should have signed the given hash.
          * @param signature Proof of signing.
-         * @returns Validity of order signature.
+         * @returns Magic bytes4 value if the signature is valid.         Magic value is bytes4(keccak256("isValidValidatorSignature(address,bytes32,address,bytes)"))
          */
         async callAsync(
             hash: string,
@@ -46,7 +46,7 @@ export class IValidatorContract extends BaseContract {
             signature: string,
             callData: Partial<CallData> = {},
             defaultBlock?: BlockParam,
-        ): Promise<boolean> {
+        ): Promise<string> {
             assert.isString('hash', hash);
             assert.isString('signerAddress', signerAddress);
             assert.isString('signature', signature);
@@ -80,7 +80,7 @@ export class IValidatorContract extends BaseContract {
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
             const abiEncoder = self._lookupAbiEncoder('isValidSignature(bytes32,address,bytes)');
             // tslint:disable boolean-naming
-            const result = abiEncoder.strictDecodeReturnValue<boolean>(rawCallResult);
+            const result = abiEncoder.strictDecodeReturnValue<string>(rawCallResult);
             // tslint:enable boolean-naming
             return result;
         },
@@ -104,18 +104,18 @@ export class IValidatorContract extends BaseContract {
             ]);
             return abiEncodedTransactionData;
         },
-        getABIDecodedTransactionData(callData: string): boolean {
+        getABIDecodedTransactionData(callData: string): string {
             const self = (this as any) as IValidatorContract;
             const abiEncoder = self._lookupAbiEncoder('isValidSignature(bytes32,address,bytes)');
             // tslint:disable boolean-naming
-            const abiDecodedCallData = abiEncoder.strictDecode<boolean>(callData);
+            const abiDecodedCallData = abiEncoder.strictDecode<string>(callData);
             return abiDecodedCallData;
         },
-        getABIDecodedReturnData(returnData: string): boolean {
+        getABIDecodedReturnData(returnData: string): string {
             const self = (this as any) as IValidatorContract;
             const abiEncoder = self._lookupAbiEncoder('isValidSignature(bytes32,address,bytes)');
             // tslint:disable boolean-naming
-            const abiDecodedReturnData = abiEncoder.strictDecodeReturnValue<boolean>(returnData);
+            const abiDecodedReturnData = abiEncoder.strictDecodeReturnValue<string>(returnData);
             return abiDecodedReturnData;
         },
     };
@@ -208,7 +208,7 @@ export class IValidatorContract extends BaseContract {
                 outputs: [
                     {
                         name: 'isValid',
-                        type: 'bool',
+                        type: 'bytes4',
                     },
                 ],
                 payable: false,
diff --git a/packages/abi-gen-wrappers/src/generated-wrappers/i_wallet.ts b/packages/abi-gen-wrappers/src/generated-wrappers/i_wallet.ts
index 042fc5ce5b..ab32fb69d1 100644
--- a/packages/abi-gen-wrappers/src/generated-wrappers/i_wallet.ts
+++ b/packages/abi-gen-wrappers/src/generated-wrappers/i_wallet.ts
@@ -37,14 +37,14 @@ export class IWalletContract extends BaseContract {
          * since they don't modify state.
          * @param hash Message hash that is signed.
          * @param signature Proof of signing.
-         * @returns Validity of order signature.
+         * @returns Magic bytes4 value if the signature is valid.         Magic value is bytes4(keccak256(&quot;isValidWalletSignature(bytes32,address,bytes)&quot;))
          */
         async callAsync(
             hash: string,
             signature: string,
             callData: Partial<CallData> = {},
             defaultBlock?: BlockParam,
-        ): Promise<boolean> {
+        ): Promise<string> {
             assert.isString('hash', hash);
             assert.isString('signature', signature);
             assert.doesConformToSchema('callData', callData, schemas.callDataSchema, [
@@ -73,7 +73,7 @@ export class IWalletContract extends BaseContract {
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
             const abiEncoder = self._lookupAbiEncoder('isValidSignature(bytes32,bytes)');
             // tslint:disable boolean-naming
-            const result = abiEncoder.strictDecodeReturnValue<boolean>(rawCallResult);
+            const result = abiEncoder.strictDecodeReturnValue<string>(rawCallResult);
             // tslint:enable boolean-naming
             return result;
         },
@@ -94,18 +94,18 @@ export class IWalletContract extends BaseContract {
             ]);
             return abiEncodedTransactionData;
         },
-        getABIDecodedTransactionData(callData: string): boolean {
+        getABIDecodedTransactionData(callData: string): string {
             const self = (this as any) as IWalletContract;
             const abiEncoder = self._lookupAbiEncoder('isValidSignature(bytes32,bytes)');
             // tslint:disable boolean-naming
-            const abiDecodedCallData = abiEncoder.strictDecode<boolean>(callData);
+            const abiDecodedCallData = abiEncoder.strictDecode<string>(callData);
             return abiDecodedCallData;
         },
-        getABIDecodedReturnData(returnData: string): boolean {
+        getABIDecodedReturnData(returnData: string): string {
             const self = (this as any) as IWalletContract;
             const abiEncoder = self._lookupAbiEncoder('isValidSignature(bytes32,bytes)');
             // tslint:disable boolean-naming
-            const abiDecodedReturnData = abiEncoder.strictDecodeReturnValue<boolean>(returnData);
+            const abiDecodedReturnData = abiEncoder.strictDecodeReturnValue<string>(returnData);
             return abiDecodedReturnData;
         },
     };
@@ -194,7 +194,7 @@ export class IWalletContract extends BaseContract {
                 outputs: [
                     {
                         name: 'isValid',
-                        type: 'bool',
+                        type: 'bytes4',
                     },
                 ],
                 payable: false,
diff --git a/packages/order-utils/src/constants.ts b/packages/order-utils/src/constants.ts
index 56573fb5ba..4f40379030 100644
--- a/packages/order-utils/src/constants.ts
+++ b/packages/order-utils/src/constants.ts
@@ -150,4 +150,6 @@ export const constants = {
     MULTI_ASSET_METHOD_ABI,
     ERC1155_METHOD_ABI,
     STATIC_CALL_METHOD_ABI,
+    IS_VALID_WALLET_SIGNATURE_MAGIC_VALUE: '0xb0671381',
+    IS_VALID_VALIDATOR_SIGNATURE_MAGIC_VALUE: '0x42b38674',
 };
diff --git a/packages/order-utils/src/signature_utils.ts b/packages/order-utils/src/signature_utils.ts
index a7d15af313..d0282aa44f 100644
--- a/packages/order-utils/src/signature_utils.ts
+++ b/packages/order-utils/src/signature_utils.ts
@@ -17,6 +17,7 @@ import * as ethUtil from 'ethereumjs-util';
 import * as _ from 'lodash';
 
 import { assert } from './assert';
+import { constants } from './constants';
 import { eip712Utils } from './eip712_utils';
 import { orderHashUtils } from './order_hash';
 import { transactionHashUtils } from './transaction_hash';
@@ -135,8 +136,8 @@ export const signatureUtils = {
         // tslint:disable-next-line:custom-no-magic-numbers
         const signatureWithoutType = signature.slice(0, -2);
         const walletContract = new IWalletContract(signerAddress, provider);
-        const isValid = await walletContract.isValidSignature.callAsync(data, signatureWithoutType);
-        return isValid;
+        const magicValue = await walletContract.isValidSignature.callAsync(data, signatureWithoutType);
+        return magicValue === constants.IS_VALID_WALLET_SIGNATURE_MAGIC_VALUE;
     },
     /**
      * Verifies that the provided validator signature is valid according to the 0x Protocol smart contracts
@@ -169,12 +170,12 @@ export const signatureUtils = {
         }
 
         const validatorContract = new IValidatorContract(signerAddress, provider);
-        const isValid = await validatorContract.isValidSignature.callAsync(
+        const magicValue = await validatorContract.isValidSignature.callAsync(
             data,
             signerAddress,
             validatorSignature.signature,
         );
-        return isValid;
+        return magicValue === constants.IS_VALID_VALIDATOR_SIGNATURE_MAGIC_VALUE;
     },
     /**
      * Checks if the supplied elliptic curve signature corresponds to signing `data` with