diff --git a/.github/workflows/nodejs.yml b/.github/workflows/nodejs.yml
index 107e0c0..de5224f 100644
--- a/.github/workflows/nodejs.yml
+++ b/.github/workflows/nodejs.yml
@@ -23,3 +23,16 @@ jobs:
       - run: yarn lint
       - run: git submodule update --init --recursive
       - run: yarn run test
+  types:
+    name: 'Test types'
+    runs-on: ubuntu-latest
+    defaults:
+      run:
+        working-directory: test/types
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-node@v4
+        with:
+          node-version: 20
+      - run: yarn
+      - run: yarn test
diff --git a/index.d.ts b/index.d.ts
index cdf2e71..05682ae 100644
--- a/index.d.ts
+++ b/index.d.ts
@@ -15,8 +15,8 @@ type Schema =
       $id?: string
       $anchor?: string
       $ref?: string
-      definitions?: { [id: string]: Schema }
-      $defs?: { [id: string]: Schema }
+      definitions?: Partial<{ [id: string]: Schema }>
+      $defs?: Partial<{ [id: string]: Schema }>
       $recursiveRef?: string
       $recursiveAnchor?: boolean
       // generic
@@ -61,15 +61,15 @@ type Schema =
       contentMediaType?: string
       contentSchema?: Schema
       // objects
-      properties?: { [id: string]: Schema }
+      properties?: Partial<{ [id: string]: Schema }>
       maxProperties?: number
       minProperties?: number
       additionalProperties?: Schema
-      patternProperties?: { [pattern: string]: Schema }
+      patternProperties?: Partial<{ [pattern: string]: Schema }>
       propertyNames?: Schema
-      dependencies?: { [id: string]: Array<string> | Schema }
-      dependentRequired?: { [id: string]: Array<string> }
-      dependentSchemas?: { [id: string]: Schema }
+      dependencies?: Partial<{ [id: string]: Array<string> | Schema }>
+      dependentRequired?: Partial<{ [id: string]: Array<string> }>
+      dependentSchemas?: Partial<{ [id: string]: Schema }>
       // see-through
       unevaluatedProperties?: Schema
       unevaluatedItems?: Schema
diff --git a/package.json b/package.json
index d4c0062..8764679 100644
--- a/package.json
+++ b/package.json
@@ -36,7 +36,8 @@
     "test": "npm run test:raw | tap-spec",
     "test:raw": "npm run test:normal && npm run test:module",
     "test:module": "tape -r ./test/tools/test-module.js test/*.js test/regressions/*.js",
-    "test:normal": "tape test/*.js test/regressions/*.js"
+    "test:normal": "tape test/*.js test/regressions/*.js",
+    "test:types": "yarn --cwd test/types test"
   },
   "dependencies": {},
   "devDependencies": {
diff --git a/test/types/package.json b/test/types/package.json
new file mode 100644
index 0000000..755eb0c
--- /dev/null
+++ b/test/types/package.json
@@ -0,0 +1,11 @@
+{
+  "name": "type-tests",
+  "private": true,
+  "devDependencies": {
+    "@types/node": "^20.11.16",
+    "typescript": "^5.3.3"
+  },
+  "scripts": {
+    "test": "tsc --noEmit"
+  }
+}
diff --git a/test/types/tests/index.ts b/test/types/tests/index.ts
new file mode 100644
index 0000000..f639754
--- /dev/null
+++ b/test/types/tests/index.ts
@@ -0,0 +1,41 @@
+import { validator } from '../../../index'
+
+const schema = {
+  type: 'object',
+  allOf: [
+    {
+      if: {
+        properties: {
+          propertyA: {
+            const: 1,
+          },
+        },
+      },
+      then: {
+        properties: {
+          propertyB: {
+            const: null,
+          },
+        },
+      },
+    },
+    {
+      if: {
+        properties: {
+          propertyA: {
+            const: 2,
+          },
+        },
+      },
+      then: {
+        properties: {
+          propertyC: {
+            const: null,
+          },
+        },
+      },
+    },
+  ],
+}
+
+const myValidator = validator(schema)
diff --git a/test/types/tsconfig.json b/test/types/tsconfig.json
new file mode 100644
index 0000000..7c465a6
--- /dev/null
+++ b/test/types/tsconfig.json
@@ -0,0 +1,7 @@
+{
+  "compilerOptions": {
+    "strict": true,
+  },
+  "include": ["tests"],
+  "exclude": ["node_modules"]
+}
diff --git a/test/types/yarn.lock b/test/types/yarn.lock
new file mode 100644
index 0000000..d3e3892
--- /dev/null
+++ b/test/types/yarn.lock
@@ -0,0 +1,20 @@
+# THIS IS AN AUTOGENERATED FILE. DO NOT EDIT THIS FILE DIRECTLY.
+# yarn lockfile v1
+
+
+"@types/node@^20.11.16":
+  version "20.11.16"
+  resolved "https://registry.yarnpkg.com/@types/node/-/node-20.11.16.tgz#4411f79411514eb8e2926f036c86c9f0e4ec6708"
+  integrity sha512-gKb0enTmRCzXSSUJDq6/sPcqrfCv2mkkG6Jt/clpn5eiCbKTY+SgZUxo+p8ZKMof5dCp9vHQUAB7wOUTod22wQ==
+  dependencies:
+    undici-types "~5.26.4"
+
+typescript@^5.3.3:
+  version "5.3.3"
+  resolved "https://registry.yarnpkg.com/typescript/-/typescript-5.3.3.tgz#b3ce6ba258e72e6305ba66f5c9b452aaee3ffe37"
+  integrity sha512-pXWcraxM0uxAS+tN0AG/BF2TyqmHO014Z070UsJ+pFvYuRSq8KH8DmWpnbXe0pEPDHXZV3FcAbJkijJ5oNEnWw==
+
+undici-types@~5.26.4:
+  version "5.26.5"
+  resolved "https://registry.yarnpkg.com/undici-types/-/undici-types-5.26.5.tgz#bcd539893d00b56e964fd2657a4866b221a65617"
+  integrity sha512-JlCMO+ehdEIKqlFxk6IfVoAUVmgz7cU7zD/h9XZ0qzeosSHmUJVOzSQvvYSYWXkFXC+IfLKSIffhv0sVZup6pA==