diff --git a/packages/bundle-size/src/utils/buildFixture.js b/packages/bundle-size/src/utils/buildFixture.js
index 99ef2578e5583..aaaa1ace517f7 100644
--- a/packages/bundle-size/src/utils/buildFixture.js
+++ b/packages/bundle-size/src/utils/buildFixture.js
@@ -129,8 +129,8 @@ module.exports = async function buildFixture(preparedFixture, quiet) {
     /* eslint-enable @typescript-eslint/naming-convention */
   ]);
 
-  await fs.writeFile(webpackOutputPath, terserOutput.code);
-  await fs.writeFile(terserOutputPath, terserOutputMinified.code);
+  await fs.writeFile(webpackOutputPath, terserOutput.code ?? '');
+  await fs.writeFile(terserOutputPath, terserOutputMinified.code ?? '');
 
   if (!quiet) {
     console.log(
diff --git a/packages/bundle-size/src/utils/prepareFixture.js b/packages/bundle-size/src/utils/prepareFixture.js
index 2a4ca190f3da3..97e1f30d80ac2 100644
--- a/packages/bundle-size/src/utils/prepareFixture.js
+++ b/packages/bundle-size/src/utils/prepareFixture.js
@@ -9,6 +9,11 @@ const ajv = new Ajv();
 /** @typedef {{ name: string }} FixtureMetadata */
 /** @typedef {{ absolutePath: string, relativePath: string, name: string }} PreparedFixture */
 
+/**
+ * @template T
+ * @typedef {NonNullable<T> & {[P in keyof T]-?: NonNullable<T[P]>;}} RequiredNonNullableRecord<T>
+ */
+
 /**
  * Prepares a fixture file to be compiled with Webpack, grabs data from a default export and removes it.
  *
@@ -59,7 +64,7 @@ module.exports = async function prepareFixture(fixture) {
 
   /**
    * @param {typeof result} value
-   * @return {value is Required<NonNullable<typeof result>> & {metadata: FixtureMetadata}}
+   * @return {value is RequiredNonNullableRecord<typeof result> & {metadata: FixtureMetadata}}
    */
   function isTransformedFixtureResultHasMetadata(value) {
     return Boolean(value && value.metadata && Object.keys(value.metadata).length);
diff --git a/scripts/exec.js b/scripts/exec.js
index 40cd4fd16bbce..1a4a1e108b909 100644
--- a/scripts/exec.js
+++ b/scripts/exec.js
@@ -42,10 +42,10 @@ function exec(cmd, displayName, cwd = process.cwd(), opts = {}) {
     );
 
     if (opts.stdout) {
-      child.stdout.pipe(opts.stdout);
+      child.stdout?.pipe(opts.stdout);
     }
     if (opts.stderr) {
-      child.stderr.pipe(opts.stderr);
+      child.stderr?.pipe(opts.stderr);
     }
   });
 }
diff --git a/tools/generators/epic-generator/index.spec.ts b/tools/generators/epic-generator/index.spec.ts
index bc0dc6c78accc..f07c47ab82526 100644
--- a/tools/generators/epic-generator/index.spec.ts
+++ b/tools/generators/epic-generator/index.spec.ts
@@ -45,7 +45,7 @@ function setupTest(packages: Package[]) {
 
   // response to 'gh auth'
   spawnSyncMock.mockReturnValueOnce({
-    output: ['Logged in to github.com'],
+    output: [['Logged in to github.com']],
   });
 
   // response to epic creation
@@ -114,7 +114,7 @@ describe('epic-generator', () => {
 
     it('requires you to have logged in with gh', () => {
       spawnSyncMock.mockReturnValueOnce({
-        output: ['You are not logged into any GitHub hosts. Run gh auth login to authenticate.'],
+        output: [['You are not logged into any GitHub hosts. Run gh auth login to authenticate.']],
       });
 
       const tree = createTreeWithEmptyWorkspace();
diff --git a/typings/json-stable-stringify-without-jsonify/index.d.ts b/typings/json-stable-stringify-without-jsonify/index.d.ts
index 2541e43c77a22..7e2ad7bffad75 100644
--- a/typings/json-stable-stringify-without-jsonify/index.d.ts
+++ b/typings/json-stable-stringify-without-jsonify/index.d.ts
@@ -1,7 +1,7 @@
 // Type definitions for json-stable-stringify-without-jsonify 1.0.1
 
 declare module 'json-stable-stringify-without-jsonify' {
-  function stringify(value: Record<string, any>, options?: Partial<Options>): Record<string, any>;
+  function stringify(value: Record<string, any>, options?: Partial<Options>): string;
 
   interface Options {
     cmp: (a: any, b: any) => any;