diff --git a/index.d.ts b/index.d.ts
index 843f8f9..f812a4c 100644
--- a/index.d.ts
+++ b/index.d.ts
@@ -31,7 +31,7 @@ export function getProperty<ObjectType, PathType extends string, DefaultValue =
 	object: ObjectType,
 	path: PathType,
 	defaultValue?: DefaultValue
-): ObjectType extends Record<string, unknown> | unknown[] ? (Get<ObjectType, PathType> extends unknown ? DefaultValue : Get<ObjectType, PathType>) : undefined;
+): ObjectType extends Record<string, unknown> | unknown[] ? (unknown extends Get<ObjectType, PathType> ? DefaultValue : Get<ObjectType, PathType>) : undefined;
 
 /**
 Set the property at the given path to the given value.
diff --git a/index.test-d.ts b/index.test-d.ts
index d33e872..53d859c 100644
--- a/index.test-d.ts
+++ b/index.test-d.ts
@@ -1,18 +1,19 @@
-import {expectType, expectAssignable} from 'tsd';
+import {expectTypeOf} from 'expect-type';
 import {getProperty, setProperty, hasProperty, deleteProperty} from './index.js';
 
-expectType<string>(getProperty({foo: {bar: 'unicorn'}}, 'foo.bar'));
-expectType<undefined>(getProperty({foo: {bar: 'a'}}, 'foo.notDefined.deep'));
-expectAssignable<string>(
+expectTypeOf(getProperty({foo: {bar: 'unicorn'}}, 'foo.bar')).toBeString();
+expectTypeOf(getProperty({foo: {bar: 'a'}}, 'foo.notDefined.deep')).toBeUndefined();
+expectTypeOf(
 	getProperty({foo: {bar: 'a'}}, 'foo.notDefined.deep', 'default value'),
-);
-expectType<string>(
+).toBeString();
+expectTypeOf(
 	getProperty({foo: {'dot.dot': 'unicorn'}}, 'foo.dot\\.dot'),
-);
+	// @ts-expect-error type-fest's `Get` not smart enough to deal with escaped dots
+).toEqualTypeOf<string>();
 
 const object = {foo: {bar: 'a'}};
-expectType<typeof object>(setProperty(object, 'foo.bar', 'b'));
+expectTypeOf(setProperty(object, 'foo.bar', 'b')).toEqualTypeOf(object);
 
-expectType<boolean>(hasProperty({foo: {bar: 'unicorn'}}, 'foo.bar'));
+expectTypeOf(hasProperty({foo: {bar: 'unicorn'}}, 'foo.bar')).toEqualTypeOf<boolean>();
 
-expectType<boolean>(deleteProperty({foo: {bar: 'a'}}, 'foo.bar'));
+expectTypeOf(deleteProperty({foo: {bar: 'a'}}, 'foo.bar')).toEqualTypeOf<boolean>();
diff --git a/package.json b/package.json
index 697cc4b..bb3b97a 100644
--- a/package.json
+++ b/package.json
@@ -16,7 +16,7 @@
 		"node": "^12.20.0 || ^14.13.1 || >=16.0.0"
 	},
 	"scripts": {
-		"test": "xo && ava && tsd",
+		"test": "xo && ava && tsc",
 		"bench": "node benchmark.js"
 	},
 	"files": [
@@ -42,7 +42,8 @@
 	"devDependencies": {
 		"ava": "^4.0.1",
 		"benchmark": "^2.1.4",
-		"tsd": "^0.19.1",
+		"expect-type": "^0.13.0",
+		"typescript": "^4.5.5",
 		"xo": "^0.47.0"
 	}
 }
diff --git a/tsconfig.json b/tsconfig.json
new file mode 100644
index 0000000..0c9966a
--- /dev/null
+++ b/tsconfig.json
@@ -0,0 +1,12 @@
+{
+	"compilerOptions": {
+		"lib": [
+			"es2020"
+		],
+		"strict": true,
+		"noEmit": true
+	},
+	"include": [
+		"*.ts"
+	]
+}