diff --git a/CHANGELOG.md b/CHANGELOG.md
index 9c49064..0fa39f3 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,9 @@ As of 12/13/2022, this repo has been renamed from "nftc-open-contracts" to "nftc
 ## Version -- 1.5.next [Not published]
 - TODO
 
+## Version -- 1.5.20
+- Implement ERC165 compliant version of ERC20.
+- Update the NFTSpecChecker and tests.
 
 ## Version -- 1.5.19
 - package lock cleanup
diff --git a/contracts/mocks/token/ERC20/MockERC20.sol b/contracts/mocks/token/ERC20/MockERC20.sol
index 6233e58..a053979 100644
--- a/contracts/mocks/token/ERC20/MockERC20.sol
+++ b/contracts/mocks/token/ERC20/MockERC20.sol
@@ -1,16 +1,16 @@
 // SPDX-License-Identifier: MIT
 pragma solidity 0.8.19;
 
-import '@openzeppelin/contracts/token/ERC20/ERC20.sol';
+import '../../../token/openzeppelin/ERC20/extensions/ERC20_165.sol';
 
 /**
- * @title MockERC20
+ * @title MockERC20_165
  * @author @NFTCulture
  */
-contract MockERC20 is ERC20 {
-    uint256 private immutable TOTAL_SUPPLY;
+contract MockERC20_165 is ERC20_165 {
+    uint256 private immutable _maxSupply;
 
-    constructor() ERC20('MockERC20', 'M20') {
-        TOTAL_SUPPLY = 1000000000;
+    constructor() ERC20('MockERC20_165', 'M20') {
+        _maxSupply = 1000000000;
     }
 }
diff --git a/contracts/token/openzeppelin/ERC20/extensions/ERC20_165.sol b/contracts/token/openzeppelin/ERC20/extensions/ERC20_165.sol
new file mode 100644
index 0000000..2b86b36
--- /dev/null
+++ b/contracts/token/openzeppelin/ERC20/extensions/ERC20_165.sol
@@ -0,0 +1,19 @@
+// SPDX-License-Identifier: MIT
+pragma solidity 0.8.19;
+
+import '@openzeppelin/contracts/token/ERC20/ERC20.sol';
+import '@openzeppelin/contracts/utils/introspection/ERC165.sol';
+
+/**
+ * @title ERC20_165
+ * @author @NiftyMike | @NFTCulture
+ * @dev ERC20 with ERC165 support tacked on, for consistency with more modern ERC specs.
+ */
+abstract contract ERC20_165 is ERC20, ERC165 {
+    function supportsInterface(bytes4 interfaceId) public view virtual override returns (bool) {
+        return
+            interfaceId == type(IERC20).interfaceId ||
+            interfaceId == type(IERC20Metadata).interfaceId ||
+            super.supportsInterface(interfaceId);
+    }
+}
diff --git a/contracts/utility/introspection/NFTSpecChecker.sol b/contracts/utility/introspection/NFTSpecChecker.sol
index 57800b3..ee04c6c 100644
--- a/contracts/utility/introspection/NFTSpecChecker.sol
+++ b/contracts/utility/introspection/NFTSpecChecker.sol
@@ -29,17 +29,17 @@ contract NFTSpecChecker {
     bytes4 constant _ERC165_CONTRACT = type(IERC165).interfaceId;
 
     /// @dev See {ERC165Checker-supportsInterface}
-    ///> 0x36372b07
+    ///> 0x36372b07 / 0xa219a025
     bytes4 constant _ERC20_CONTRACT = type(IERC20).interfaceId;
     bytes4 constant _ERC20_CONTRACT_METADATA = type(IERC20Metadata).interfaceId;
 
     /// @dev See {ERC165Checker-supportsInterface}
-    ///> 0x80ac58cd
+    ///> 0x80ac58cd / 0x5b5e139f
     bytes4 constant _ERC721_CONTRACT = type(IERC721).interfaceId;
     bytes4 constant _ERC721_CONTRACT_METADATA = type(IERC721Metadata).interfaceId;
 
     /// @dev See {ERC165Checker-supportsInterface}
-    ///> 0xd9b67a26
+    ///> 0xd9b67a26 / 0x0e89341c
     bytes4 constant _ERC1155_CONTRACT = type(IERC1155).interfaceId;
     bytes4 constant _ERC1155_CONTRACT_METADATA_URI = type(IERC1155MetadataURI).interfaceId;
 
@@ -56,8 +56,8 @@ contract NFTSpecChecker {
             _checkContract(targetContract, _ERC20_CONTRACT) && _checkContract(targetContract, _ERC20_CONTRACT_METADATA);
     }
 
-    function getERC20Code() external pure returns (string memory) {
-        return bytes4ToString(_ERC20_CONTRACT);
+    function getERC20Codes() external pure returns (string memory, string memory) {
+        return (bytes4ToString(_ERC20_CONTRACT), bytes4ToString(_ERC20_CONTRACT_METADATA));
     }
 
     function checkERC721(address targetContract) external view returns (bool) {
@@ -66,8 +66,8 @@ contract NFTSpecChecker {
             _checkContract(targetContract, _ERC721_CONTRACT_METADATA);
     }
 
-    function getERC721Code() external pure returns (string memory) {
-        return bytes4ToString(_ERC721_CONTRACT);
+    function getERC721Codes() external pure returns (string memory, string memory) {
+        return (bytes4ToString(_ERC721_CONTRACT), bytes4ToString(_ERC721_CONTRACT_METADATA));
     }
 
     function checkERC1155(address targetContract) external view returns (bool) {
@@ -76,8 +76,8 @@ contract NFTSpecChecker {
             _checkContract(targetContract, _ERC1155_CONTRACT_METADATA_URI);
     }
 
-    function getERC1155Code() external pure returns (string memory) {
-        return bytes4ToString(_ERC1155_CONTRACT);
+    function getERC1155Codes() external pure returns (string memory, string memory) {
+        return (bytes4ToString(_ERC1155_CONTRACT), bytes4ToString(_ERC1155_CONTRACT_METADATA_URI));
     }
 
     function checkERC2981(address targetContract) external view returns (bool) {
diff --git a/package.json b/package.json
index b0d1dd3..2bf8014 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
     "name": "@nftculture/nftc-contracts",
-    "version": "1.5.19",
+    "version": "1.5.20",
     "description": "NFTCulture Open Source Contracts Project",
     "author": "@NFTCulture",
     "license": "MIT",
diff --git a/test/contracts/utility/introspection/NFTSpecChecker.test.ts b/test/contracts/utility/introspection/NFTSpecChecker.test.ts
index 8eb60e7..e8740ca 100644
--- a/test/contracts/utility/introspection/NFTSpecChecker.test.ts
+++ b/test/contracts/utility/introspection/NFTSpecChecker.test.ts
@@ -10,7 +10,7 @@ dotenv.config();
 
 const TESTHARNESS_CONTRACT_NAME = 'TemplateTestHarness';
 const SPEC_CHECKER_CONTRACT_NAME = 'NFTSpecChecker';
-const MOCK_E20_CONTRACT_NAME = 'MockERC20';
+const MOCK_E20_CONTRACT_NAME = 'MockERC20_165';
 const MOCK_E721AB_CONTRACT_NAME = 'MockERC721ABurnable';
 const MOCK_E1155_CONTRACT_NAME = 'MockERC1155';
 
@@ -91,14 +91,17 @@ describe(`File:${__filename}\nContract: ${TESTHARNESS_CONTRACT_NAME}\n`, functio
 
     context('Spec Checker:', function () {
         it('uses valid interface codes', async function () {
-            const erc20Code = await _specCheckerInstance.connect(this.owner).getERC20Code();
+            const [erc20Code, erc20MetadataCode] = await _specCheckerInstance.connect(this.owner).getERC20Codes();
             expect(erc20Code).to.equal('0x36372b07');
+            expect(erc20MetadataCode).to.equal('0xa219a025');
 
-            const erc721Code = await _specCheckerInstance.connect(this.owner).getERC721Code();
+            const [erc721Code, erc721MetadataCode] = await _specCheckerInstance.connect(this.owner).getERC721Codes();
             expect(erc721Code).to.equal('0x80ac58cd');
+            expect(erc721MetadataCode).to.equal('0x5b5e139f');
 
-            const erc1155Code = await _specCheckerInstance.connect(this.owner).getERC1155Code();
+            const [erc1155Code, erc1155MetadataCode] = await _specCheckerInstance.connect(this.owner).getERC1155Codes();
             expect(erc1155Code).to.equal('0xd9b67a26');
+            expect(erc1155MetadataCode).to.equal('0x0e89341c');
 
             const erc2981Code = await _specCheckerInstance.connect(this.owner).getERC2981Code();
             expect(erc2981Code).to.equal('0x2a55205a');
@@ -107,7 +110,7 @@ describe(`File:${__filename}\nContract: ${TESTHARNESS_CONTRACT_NAME}\n`, functio
             expect(erc7572Code).to.equal('0xe8a3d485');
         });
 
-        it.skip('can validate ERC20s.', async function () {
+        it('can validate ERC20s.', async function () {
             // NOTE: Technically OZ ERC20 doesn't implement ERC165. Hopefully at some point they fix this.
             const result = await _specCheckerInstance.connect(this.owner).checkERC20(_mockERC20Instance.address);