ts-jest leaking @types/jest types

jest.config.json

{
	"testEnvironment": "node",
	"testRegex": ".+\\.spec\\.ts$",
	"transform": {
		"^.+\\.ts$": "ts-jest"
	},
	"injectGlobals": false
}

package.json

{
	"name": "sample",
	"version": "0.0.0",
	"private": true,
	"scripts": {
		"build": "tsc --project tsconfig.build.json",
		"test": "jest"
	},
	"devDependencies": {
		"@jest/globals": "^26.6.0",
		"jest": "^26.6.0",
		"jest-circus": "^26.6.0",
		"ts-jest": "^26.5.0",
		"typescript": "~4.1.0"
	}
}

sample.spec.ts

import { Sample } from './sample';

describe('sample test', () => {
	it('is instantiable', () => {
		expect(new Sample()).toBeInstanceOf(Sample);
	});
});

sample.ts

export class Sample { }

describe('sample', () => {
	it('is instantiable', () => {
		expect(new Sample()).toBeInstanceOf(Sample);
	});
});

tsconfig.build.json

{
	"extends": "./tsconfig.json",
	"exclude": [
		"node_modules/",
		"**/*.spec.ts"
	]
}

tsconfig.json

{
	"compilerOptions": {
		"target": "ES6",
		"module": "CommonJS",
		"lib": [
			"ES6"
		],
			
		"noEmit": false,

		"moduleResolution": "Node",

		"declaration": true,
		"sourceMap": true,

		"strict": true,
		"skipLibCheck": true
	},
	"exclude": [
		"node_modules/"
	]
}