diff --git a/package-lock.json b/package-lock.json
index 0a32b9b5b..070ad986f 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -1,12 +1,12 @@
 {
   "name": "opensea-js",
-  "version": "4.0.15",
+  "version": "4.0.19",
   "lockfileVersion": 2,
   "requires": true,
   "packages": {
     "": {
       "name": "opensea-js",
-      "version": "4.0.15",
+      "version": "4.0.19",
       "license": "MIT",
       "dependencies": {
         "@opensea/seaport-js": "^1.0.10",
diff --git a/package.json b/package.json
index c70faf44f..6db0a6a87 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "opensea-js",
-  "version": "4.0.18",
+  "version": "4.0.19",
   "description": "JavaScript SDK for the OpenSea marketplace. Let users buy or sell crypto collectibles and other cryptogoods, all on your own site!",
   "license": "MIT",
   "author": "OpenSea Developers",
diff --git a/src/__tests__/utils/utils.ts b/src/__tests__/utils/utils.ts
new file mode 100644
index 000000000..5a0919afc
--- /dev/null
+++ b/src/__tests__/utils/utils.ts
@@ -0,0 +1,30 @@
+import {
+  CROSS_CHAIN_SEAPORT_ADDRESS,
+  CROSS_CHAIN_SEAPORT_V1_4_ADDRESS,
+} from "@opensea/seaport-js/lib/constants";
+import { assert } from "chai";
+import { suite, test } from "mocha";
+import Web3 from "web3";
+import { isValidProtocol } from "../../utils/utils";
+
+suite("Utils: utils", () => {
+  test("isValidProtocol works with all forms of address", async () => {
+    const seaport_v1_1 = CROSS_CHAIN_SEAPORT_ADDRESS;
+    const seaport_v_1_4 = CROSS_CHAIN_SEAPORT_V1_4_ADDRESS;
+    const randomAddress = "0x1F7Cf51573Bf5270323a395F0bb5Fd3c3a4DB867";
+
+    assert.isTrue(isValidProtocol(seaport_v1_1));
+    assert.isTrue(isValidProtocol(seaport_v_1_4));
+    assert.isFalse(isValidProtocol(randomAddress));
+
+    assert.isTrue(isValidProtocol(seaport_v1_1.toLowerCase()));
+    assert.isTrue(isValidProtocol(seaport_v_1_4.toLowerCase()));
+    assert.isFalse(isValidProtocol(randomAddress.toLowerCase()));
+
+    assert.isTrue(isValidProtocol(Web3.utils.toChecksumAddress(seaport_v1_1)));
+    assert.isTrue(isValidProtocol(Web3.utils.toChecksumAddress(seaport_v_1_4)));
+    assert.isFalse(
+      isValidProtocol(Web3.utils.toChecksumAddress(randomAddress))
+    );
+  });
+});
diff --git a/src/utils/utils.ts b/src/utils/utils.ts
index a96289a48..f2b95b3cf 100644
--- a/src/utils/utils.ts
+++ b/src/utils/utils.ts
@@ -1145,6 +1145,6 @@ export const isValidProtocol = (protocolAddress: string): boolean => {
   const validProtocolAddresses = [
     CROSS_CHAIN_SEAPORT_ADDRESS,
     CROSS_CHAIN_SEAPORT_V1_4_ADDRESS,
-  ];
+  ].map((address) => Web3.utils.toChecksumAddress(address));
   return validProtocolAddresses.includes(checkSumAddress);
 };