diff --git a/__tests__/main.test.ts b/__tests__/main.test.ts
index 079ac14..03b68e4 100644
--- a/__tests__/main.test.ts
+++ b/__tests__/main.test.ts
@@ -283,6 +283,24 @@ describe('action', () => {
     }
   });
 
+  it('fails if schema missing $schema key', async () => {
+    mockGetBooleanInput({});
+    mockGetInput({ schema });
+    mockGetMultilineInput({ files });
+
+    jest
+      .mocked(fs.readFile)
+      .mockResolvedValueOnce(schemaContents.replace('$schema', '_schema'));
+
+    await main.run();
+    expect(runSpy).toHaveReturned();
+    expect(process.exitCode).not.toBeDefined();
+
+    expect(core.setFailed).toHaveBeenLastCalledWith(
+      'JSON schema missing $schema key'
+    );
+  });
+
   it('fails if no files to validate', async () => {
     mockGetBooleanInput({});
     mockGetInput({ schema });
@@ -377,4 +395,28 @@ describe('action', () => {
     expect(core.debug).toHaveBeenCalledWith(`𐄂 ${paths[0]} is not valid`);
     expect(core.debug).toHaveBeenCalledWith(`✓ ${paths[1]} is valid`);
   });
+
+  it('supports JSON Schema draft-04', async () => {
+    mockGetBooleanInput({});
+    mockGetInput({ schema });
+    mockGetMultilineInput({ files });
+
+    jest
+      .mocked(fs.readFile)
+      .mockResolvedValueOnce(
+        schemaContents.replace(
+          'http://json-schema.org/draft-07/schema#',
+          'http://json-schema.org/draft-04/schema#'
+        )
+      )
+      .mockResolvedValueOnce(instanceContents);
+    mockGlobGenerator(['/foo/bar/baz/config.yml']);
+
+    await main.run();
+    expect(runSpy).toHaveReturned();
+    expect(process.exitCode).not.toBeDefined();
+
+    expect(core.setOutput).toHaveBeenCalledTimes(1);
+    expect(core.setOutput).toHaveBeenLastCalledWith('valid', true);
+  });
 });
diff --git a/dist/index.js b/dist/index.js
index 6f231e9..fff098f 100644
--- a/dist/index.js
+++ b/dist/index.js
@@ -45230,6 +45230,225 @@ exports.VERSION = '1.7.0';
 
 /***/ }),
 
+/***/ 7023:
+/***/ ((module, exports, __nccwpck_require__) => {
+
+"use strict";
+
+Object.defineProperty(exports, "__esModule", ({ value: true }));
+exports.CodeGen = exports.Name = exports.nil = exports.stringify = exports.str = exports._ = exports.KeywordCxt = void 0;
+const core_1 = __nccwpck_require__(2685);
+const draft4_1 = __nccwpck_require__(2589);
+const discriminator_1 = __nccwpck_require__(4025);
+const draft4MetaSchema = __nccwpck_require__(8978);
+const META_SUPPORT_DATA = ["/properties"];
+const META_SCHEMA_ID = "http://json-schema.org/draft-04/schema";
+class Ajv extends core_1.default {
+    constructor(opts = {}) {
+        super({
+            ...opts,
+            schemaId: "id",
+        });
+    }
+    _addVocabularies() {
+        super._addVocabularies();
+        draft4_1.default.forEach((v) => this.addVocabulary(v));
+        if (this.opts.discriminator)
+            this.addKeyword(discriminator_1.default);
+    }
+    _addDefaultMetaSchema() {
+        super._addDefaultMetaSchema();
+        if (!this.opts.meta)
+            return;
+        const metaSchema = this.opts.$data
+            ? this.$dataMetaSchema(draft4MetaSchema, META_SUPPORT_DATA)
+            : draft4MetaSchema;
+        this.addMetaSchema(metaSchema, META_SCHEMA_ID, false);
+        this.refs["http://json-schema.org/schema"] = META_SCHEMA_ID;
+    }
+    defaultMeta() {
+        return (this.opts.defaultMeta =
+            super.defaultMeta() || (this.getSchema(META_SCHEMA_ID) ? META_SCHEMA_ID : undefined));
+    }
+}
+module.exports = exports = Ajv;
+Object.defineProperty(exports, "__esModule", ({ value: true }));
+exports["default"] = Ajv;
+var core_2 = __nccwpck_require__(2685);
+Object.defineProperty(exports, "KeywordCxt", ({ enumerable: true, get: function () { return core_2.KeywordCxt; } }));
+var core_3 = __nccwpck_require__(2685);
+Object.defineProperty(exports, "_", ({ enumerable: true, get: function () { return core_3._; } }));
+Object.defineProperty(exports, "str", ({ enumerable: true, get: function () { return core_3.str; } }));
+Object.defineProperty(exports, "stringify", ({ enumerable: true, get: function () { return core_3.stringify; } }));
+Object.defineProperty(exports, "nil", ({ enumerable: true, get: function () { return core_3.nil; } }));
+Object.defineProperty(exports, "Name", ({ enumerable: true, get: function () { return core_3.Name; } }));
+Object.defineProperty(exports, "CodeGen", ({ enumerable: true, get: function () { return core_3.CodeGen; } }));
+//# sourceMappingURL=index.js.map
+
+/***/ }),
+
+/***/ 4935:
+/***/ ((__unused_webpack_module, exports, __nccwpck_require__) => {
+
+"use strict";
+
+Object.defineProperty(exports, "__esModule", ({ value: true }));
+const ref_1 = __nccwpck_require__(6532);
+const core = [
+    "$schema",
+    "id",
+    "$defs",
+    { keyword: "$comment" },
+    "definitions",
+    ref_1.default,
+];
+exports["default"] = core;
+//# sourceMappingURL=core.js.map
+
+/***/ }),
+
+/***/ 2589:
+/***/ ((__unused_webpack_module, exports, __nccwpck_require__) => {
+
+"use strict";
+
+Object.defineProperty(exports, "__esModule", ({ value: true }));
+const core_1 = __nccwpck_require__(4935);
+const validation_1 = __nccwpck_require__(3035);
+const applicator_1 = __nccwpck_require__(3048);
+const format_1 = __nccwpck_require__(9841);
+const metadataVocabulary = ["title", "description", "default"];
+const draft4Vocabularies = [
+    core_1.default,
+    validation_1.default,
+    applicator_1.default(),
+    format_1.default,
+    metadataVocabulary,
+];
+exports["default"] = draft4Vocabularies;
+//# sourceMappingURL=draft4.js.map
+
+/***/ }),
+
+/***/ 3035:
+/***/ ((__unused_webpack_module, exports, __nccwpck_require__) => {
+
+"use strict";
+
+Object.defineProperty(exports, "__esModule", ({ value: true }));
+const limitNumber_1 = __nccwpck_require__(45);
+const limitNumberExclusive_1 = __nccwpck_require__(2674);
+const multipleOf_1 = __nccwpck_require__(3201);
+const limitLength_1 = __nccwpck_require__(7598);
+const pattern_1 = __nccwpck_require__(4960);
+const limitProperties_1 = __nccwpck_require__(3470);
+const required_1 = __nccwpck_require__(3602);
+const limitItems_1 = __nccwpck_require__(3924);
+const uniqueItems_1 = __nccwpck_require__(9351);
+const const_1 = __nccwpck_require__(3694);
+const enum_1 = __nccwpck_require__(5529);
+const validation = [
+    // number
+    limitNumber_1.default,
+    limitNumberExclusive_1.default,
+    multipleOf_1.default,
+    // string
+    limitLength_1.default,
+    pattern_1.default,
+    // object
+    limitProperties_1.default,
+    required_1.default,
+    // array
+    limitItems_1.default,
+    uniqueItems_1.default,
+    // any
+    { keyword: "type", schemaType: ["string", "array"] },
+    { keyword: "nullable", schemaType: "boolean" },
+    const_1.default,
+    enum_1.default,
+];
+exports["default"] = validation;
+//# sourceMappingURL=index.js.map
+
+/***/ }),
+
+/***/ 45:
+/***/ ((__unused_webpack_module, exports, __nccwpck_require__) => {
+
+"use strict";
+
+Object.defineProperty(exports, "__esModule", ({ value: true }));
+const core_1 = __nccwpck_require__(2685);
+const codegen_1 = __nccwpck_require__(9179);
+const ops = codegen_1.operators;
+const KWDs = {
+    maximum: {
+        exclusive: "exclusiveMaximum",
+        ops: [
+            { okStr: "<=", ok: ops.LTE, fail: ops.GT },
+            { okStr: "<", ok: ops.LT, fail: ops.GTE },
+        ],
+    },
+    minimum: {
+        exclusive: "exclusiveMinimum",
+        ops: [
+            { okStr: ">=", ok: ops.GTE, fail: ops.LT },
+            { okStr: ">", ok: ops.GT, fail: ops.LTE },
+        ],
+    },
+};
+const error = {
+    message: (cxt) => core_1.str `must be ${kwdOp(cxt).okStr} ${cxt.schemaCode}`,
+    params: (cxt) => core_1._ `{comparison: ${kwdOp(cxt).okStr}, limit: ${cxt.schemaCode}}`,
+};
+const def = {
+    keyword: Object.keys(KWDs),
+    type: "number",
+    schemaType: "number",
+    $data: true,
+    error,
+    code(cxt) {
+        const { data, schemaCode } = cxt;
+        cxt.fail$data(core_1._ `${data} ${kwdOp(cxt).fail} ${schemaCode} || isNaN(${data})`);
+    },
+};
+function kwdOp(cxt) {
+    var _a;
+    const keyword = cxt.keyword;
+    const opsIdx = ((_a = cxt.parentSchema) === null || _a === void 0 ? void 0 : _a[KWDs[keyword].exclusive]) ? 1 : 0;
+    return KWDs[keyword].ops[opsIdx];
+}
+exports["default"] = def;
+//# sourceMappingURL=limitNumber.js.map
+
+/***/ }),
+
+/***/ 2674:
+/***/ ((__unused_webpack_module, exports) => {
+
+"use strict";
+
+Object.defineProperty(exports, "__esModule", ({ value: true }));
+const KWDs = {
+    exclusiveMaximum: "maximum",
+    exclusiveMinimum: "minimum",
+};
+const def = {
+    keyword: Object.keys(KWDs),
+    type: "number",
+    schemaType: "boolean",
+    code({ keyword, parentSchema }) {
+        const limitKwd = KWDs[keyword];
+        if (parentSchema[limitKwd] === undefined) {
+            throw new Error(`${keyword} can only be used with ${limitKwd}`);
+        }
+    },
+};
+exports["default"] = def;
+//# sourceMappingURL=limitNumberExclusive.js.map
+
+/***/ }),
+
 /***/ 407:
 /***/ ((__unused_webpack_module, exports) => {
 
@@ -89404,6 +89623,7 @@ const core = __importStar(__nccwpck_require__(2186));
 const glob = __importStar(__nccwpck_require__(8090));
 const http = __importStar(__nccwpck_require__(6255));
 const _2019_1 = __importDefault(__nccwpck_require__(5988));
+const ajv_draft_04_1 = __importDefault(__nccwpck_require__(7023));
 const ajv_formats_1 = __importDefault(__nccwpck_require__(567));
 const yaml = __importStar(__nccwpck_require__(4083));
 /**
@@ -89416,6 +89636,7 @@ async function run() {
         const files = core.getMultilineInput('files', { required: true });
         const cacheRemoteSchema = core.getBooleanInput('cache-remote-schema');
         const failOnInvalid = core.getBooleanInput('fail-on-invalid');
+        // TODO - Handle special case where schemaPath === 'json-schema', then use ajv.validateSchema
         // Fetch and cache remote schemas
         if (schemaPath.startsWith('http://') || schemaPath.startsWith('https://')) {
             const schemaUrl = schemaPath;
@@ -89454,12 +89675,19 @@ async function run() {
             }
         }
         // Load and compile the schema
-        const schema = yaml.parse(await fs.readFile(schemaPath, 'utf-8'));
-        const ajv = new _2019_1.default();
-        /* eslint-disable @typescript-eslint/no-require-imports, @typescript-eslint/no-var-requires */
-        ajv.addMetaSchema(__nccwpck_require__(18));
-        ajv.addMetaSchema(__nccwpck_require__(98));
-        /* eslint-enable @typescript-eslint/no-require-imports, @typescript-eslint/no-var-requires */
+        const schema = JSON.parse(await fs.readFile(schemaPath, 'utf-8'));
+        if (typeof schema.$schema !== 'string') {
+            core.setFailed('JSON schema missing $schema key');
+            return;
+        }
+        const draft04Schema = schema.$schema === 'http://json-schema.org/draft-04/schema#';
+        const ajv = draft04Schema ? new ajv_draft_04_1.default() : new _2019_1.default();
+        if (!draft04Schema) {
+            /* eslint-disable @typescript-eslint/no-require-imports, @typescript-eslint/no-var-requires */
+            ajv.addMetaSchema(__nccwpck_require__(18));
+            ajv.addMetaSchema(__nccwpck_require__(98));
+            /* eslint-enable @typescript-eslint/no-require-imports, @typescript-eslint/no-var-requires */
+        }
         const validate = (0, ajv_formats_1.default)(ajv).compile(schema);
         let valid = true;
         let filesValidated = false;
@@ -91412,7 +91640,7 @@ var YAMLMap = __nccwpck_require__(6011);
 var YAMLSeq = __nccwpck_require__(5161);
 var resolveBlockMap = __nccwpck_require__(2986);
 var resolveBlockSeq = __nccwpck_require__(2289);
-var resolveFlowCollection = __nccwpck_require__(45);
+var resolveFlowCollection = __nccwpck_require__(5488);
 
 function resolveCollection(CN, ctx, token, onError, tagName, tag) {
     const coll = token.type === 'block-map'
@@ -92387,7 +92615,7 @@ exports.resolveEnd = resolveEnd;
 
 /***/ }),
 
-/***/ 45:
+/***/ 5488:
 /***/ ((__unused_webpack_module, exports, __nccwpck_require__) => {
 
 "use strict";
@@ -99821,6 +100049,14 @@ exports.visit = visit;
 exports.visitAsync = visitAsync;
 
 
+/***/ }),
+
+/***/ 8978:
+/***/ ((module) => {
+
+"use strict";
+module.exports = JSON.parse('{"id":"http://json-schema.org/draft-04/schema#","$schema":"http://json-schema.org/draft-04/schema#","description":"Core schema meta-schema","definitions":{"schemaArray":{"type":"array","minItems":1,"items":{"$ref":"#"}},"positiveInteger":{"type":"integer","minimum":0},"positiveIntegerDefault0":{"allOf":[{"$ref":"#/definitions/positiveInteger"},{"default":0}]},"simpleTypes":{"enum":["array","boolean","integer","null","number","object","string"]},"stringArray":{"type":"array","items":{"type":"string"},"minItems":1,"uniqueItems":true}},"type":"object","properties":{"id":{"type":"string","format":"uri"},"$schema":{"type":"string","format":"uri"},"title":{"type":"string"},"description":{"type":"string"},"default":{},"multipleOf":{"type":"number","minimum":0,"exclusiveMinimum":true},"maximum":{"type":"number"},"exclusiveMaximum":{"type":"boolean","default":false},"minimum":{"type":"number"},"exclusiveMinimum":{"type":"boolean","default":false},"maxLength":{"$ref":"#/definitions/positiveInteger"},"minLength":{"$ref":"#/definitions/positiveIntegerDefault0"},"pattern":{"type":"string","format":"regex"},"additionalItems":{"anyOf":[{"type":"boolean"},{"$ref":"#"}],"default":{}},"items":{"anyOf":[{"$ref":"#"},{"$ref":"#/definitions/schemaArray"}],"default":{}},"maxItems":{"$ref":"#/definitions/positiveInteger"},"minItems":{"$ref":"#/definitions/positiveIntegerDefault0"},"uniqueItems":{"type":"boolean","default":false},"maxProperties":{"$ref":"#/definitions/positiveInteger"},"minProperties":{"$ref":"#/definitions/positiveIntegerDefault0"},"required":{"$ref":"#/definitions/stringArray"},"additionalProperties":{"anyOf":[{"type":"boolean"},{"$ref":"#"}],"default":{}},"definitions":{"type":"object","additionalProperties":{"$ref":"#"},"default":{}},"properties":{"type":"object","additionalProperties":{"$ref":"#"},"default":{}},"patternProperties":{"type":"object","additionalProperties":{"$ref":"#"},"default":{}},"dependencies":{"type":"object","additionalProperties":{"anyOf":[{"$ref":"#"},{"$ref":"#/definitions/stringArray"}]}},"enum":{"type":"array","minItems":1,"uniqueItems":true},"type":{"anyOf":[{"$ref":"#/definitions/simpleTypes"},{"type":"array","items":{"$ref":"#/definitions/simpleTypes"},"minItems":1,"uniqueItems":true}]},"allOf":{"$ref":"#/definitions/schemaArray"},"anyOf":{"$ref":"#/definitions/schemaArray"},"oneOf":{"$ref":"#/definitions/schemaArray"},"not":{"$ref":"#"}},"dependencies":{"exclusiveMaximum":["maximum"],"exclusiveMinimum":["minimum"]},"default":{}}');
+
 /***/ }),
 
 /***/ 4775:
diff --git a/dist/licenses.txt b/dist/licenses.txt
index 39fbe7a..71369f8 100644
--- a/dist/licenses.txt
+++ b/dist/licenses.txt
@@ -571,6 +571,31 @@ SOFTWARE.
 
 
 
+ajv-draft-04
+MIT
+MIT License
+
+Copyright (c) 2021 Evgeny Poberezkin
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+
+
 ajv-formats
 MIT
 MIT License
diff --git a/package-lock.json b/package-lock.json
index 83fb35f..40a360f 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -14,6 +14,7 @@
         "@actions/glob": "^0.4.0",
         "@actions/http-client": "^2.2.0",
         "ajv": "^8.12.0",
+        "ajv-draft-04": "^1.0.0",
         "ajv-formats": "^2.1.1",
         "yaml": "^2.3.4"
       },
@@ -2048,6 +2049,19 @@
         "url": "https://github.com/sponsors/epoberezkin"
       }
     },
+    "node_modules/ajv-draft-04": {
+      "version": "1.0.0",
+      "resolved": "https://registry.npmjs.org/ajv-draft-04/-/ajv-draft-04-1.0.0.tgz",
+      "integrity": "sha512-mv00Te6nmYbRp5DCwclxtt7yV/joXJPGS7nM+97GdxvuttCOfgI3K4U25zboyeX0O+myI8ERluxQe5wljMmVIw==",
+      "peerDependencies": {
+        "ajv": "^8.5.0"
+      },
+      "peerDependenciesMeta": {
+        "ajv": {
+          "optional": true
+        }
+      }
+    },
     "node_modules/ajv-formats": {
       "version": "2.1.1",
       "resolved": "https://registry.npmjs.org/ajv-formats/-/ajv-formats-2.1.1.tgz",
diff --git a/package.json b/package.json
index 8f59ab5..9a90395 100644
--- a/package.json
+++ b/package.json
@@ -72,6 +72,7 @@
     "@actions/glob": "^0.4.0",
     "@actions/http-client": "^2.2.0",
     "ajv": "^8.12.0",
+    "ajv-draft-04": "^1.0.0",
     "ajv-formats": "^2.1.1",
     "yaml": "^2.3.4"
   },
diff --git a/src/main.ts b/src/main.ts
index 982447b..61bdb33 100644
--- a/src/main.ts
+++ b/src/main.ts
@@ -8,6 +8,7 @@ import * as glob from '@actions/glob';
 import * as http from '@actions/http-client';
 
 import Ajv2019 from 'ajv/dist/2019';
+import AjvDraft04 from 'ajv-draft-04';
 import AjvFormats from 'ajv-formats';
 import * as yaml from 'yaml';
 
@@ -72,12 +73,27 @@ export async function run(): Promise<void> {
     }
 
     // Load and compile the schema
-    const schema = yaml.parse(await fs.readFile(schemaPath, 'utf-8'));
-    const ajv = new Ajv2019();
-    /* eslint-disable @typescript-eslint/no-require-imports, @typescript-eslint/no-var-requires */
-    ajv.addMetaSchema(require('ajv/dist/refs/json-schema-draft-06.json'));
-    ajv.addMetaSchema(require('ajv/dist/refs/json-schema-draft-07.json'));
-    /* eslint-enable @typescript-eslint/no-require-imports, @typescript-eslint/no-var-requires */
+    const schema: Record<string, unknown> = JSON.parse(
+      await fs.readFile(schemaPath, 'utf-8')
+    );
+
+    if (typeof schema.$schema !== 'string') {
+      core.setFailed('JSON schema missing $schema key');
+      return;
+    }
+
+    const draft04Schema =
+      schema.$schema === 'http://json-schema.org/draft-04/schema#';
+
+    const ajv = draft04Schema ? new AjvDraft04() : new Ajv2019();
+
+    if (!draft04Schema) {
+      /* eslint-disable @typescript-eslint/no-require-imports, @typescript-eslint/no-var-requires */
+      ajv.addMetaSchema(require('ajv/dist/refs/json-schema-draft-06.json'));
+      ajv.addMetaSchema(require('ajv/dist/refs/json-schema-draft-07.json'));
+      /* eslint-enable @typescript-eslint/no-require-imports, @typescript-eslint/no-var-requires */
+    }
+
     const validate = AjvFormats(ajv).compile(schema);
 
     let valid = true;