diff --git a/.eslintignore b/.eslintignore
index a130f8b70..d32e28f33 100644
--- a/.eslintignore
+++ b/.eslintignore
@@ -863,6 +863,7 @@ packages/tools/buildServerDocker.js
 packages/tools/buildServerDocker.test.js
 packages/tools/bundleDefaultPlugins.js
 packages/tools/bundleDefaultPlugins.test.js
+packages/tools/checkIgnoredFiles.js
 packages/tools/checkLibPaths.js
 packages/tools/checkLibPaths.test.js
 packages/tools/convertThemesToCss.js
diff --git a/.github/scripts/run_ci.sh b/.github/scripts/run_ci.sh
index 5d218d294..3c42913cb 100755
--- a/.github/scripts/run_ci.sh
+++ b/.github/scripts/run_ci.sh
@@ -153,6 +153,24 @@ if [ "$IS_PULL_REQUEST" == "1" ] || [ "$IS_DEV_BRANCH" = "1" ]; then
 	fi
 fi
 
+# =============================================================================
+# Check .gitignore and .eslintignore files - they should be updated when
+# new TypeScript files are added by running `yarn run updateIgnored`.
+# See coding_style.md
+# =============================================================================
+
+if [ "$IS_PULL_REQUEST" == "1" ]; then
+	if [ "$IS_LINUX" == "1" ]; then
+		echo "Step: Checking for files that should have been ignored..."
+
+		node packages/tools/checkIgnoredFiles.js 
+		testResult=$?
+		if [ $testResult -ne 0 ]; then
+			exit $testResult
+		fi
+	fi
+fi
+
 # =============================================================================
 # Find out if we should run the build or not. Electron-builder gets stuck when
 # building PRs so we disable it in this case. The Linux build should provide
diff --git a/.gitignore b/.gitignore
index cfeb31adb..4ef50cb79 100644
--- a/.gitignore
+++ b/.gitignore
@@ -848,6 +848,7 @@ packages/tools/buildServerDocker.js
 packages/tools/buildServerDocker.test.js
 packages/tools/bundleDefaultPlugins.js
 packages/tools/bundleDefaultPlugins.test.js
+packages/tools/checkIgnoredFiles.js
 packages/tools/checkLibPaths.js
 packages/tools/checkLibPaths.test.js
 packages/tools/convertThemesToCss.js
diff --git a/lint-staged.config.js b/lint-staged.config.js
index 477b0b8bf..ffba84cdd 100644
--- a/lint-staged.config.js
+++ b/lint-staged.config.js
@@ -13,5 +13,6 @@ module.exports = {
 	'*.{js,jsx,ts,tsx}': [
 		'yarn run linter-precommit',
 		'yarn run checkLibPaths',
+		'node packages/tools/checkIgnoredFiles.js',
 	],
 };
diff --git a/packages/tools/checkIgnoredFiles.ts b/packages/tools/checkIgnoredFiles.ts
new file mode 100644
index 000000000..cda55e8be
--- /dev/null
+++ b/packages/tools/checkIgnoredFiles.ts
@@ -0,0 +1,33 @@
+import { execCommand, getRootDir } from '@joplin/utils';
+import { readFile, writeFile } from 'fs-extra';
+import { chdir } from 'process';
+
+const main = async () => {
+	chdir(await getRootDir());
+
+	const previousContent = {
+		'.gitignore': await readFile('.gitignore', 'utf8'),
+		'.eslintignore': await readFile('.eslintignore', 'utf8'),
+	};
+
+	await execCommand('yarn run updateIgnored', { quiet: true });
+
+	const newContent = {
+		'.gitignore': await readFile('.gitignore', 'utf8'),
+		'.eslintignore': await readFile('.eslintignore', 'utf8'),
+	};
+
+	if (newContent['.gitignore'] !== previousContent['.gitignore'] || newContent['.eslintignore'] !== previousContent['.eslintignore']) {
+		await writeFile('.gitignore', previousContent['.gitignore'], 'utf8');
+		await writeFile('.eslintignore', previousContent['.eslintignore'], 'utf8');
+		throw new Error('.gitignore or .eslintignore would be modified - run `yarn run updateIgnored`');
+	}
+};
+
+if (require.main === module) {
+// eslint-disable-next-line promise/prefer-await-to-then -- Old code before rule was applied
+	main().catch((error) => {
+		console.error(error);
+		process.exit(1);
+	});
+}