diff --git a/packages/dev/config/eslint.js b/packages/dev/config/eslint.js
index 646abcf..f881d36 100644
--- a/packages/dev/config/eslint.js
+++ b/packages/dev/config/eslint.js
@@ -10,7 +10,6 @@ import standardConfig from 'eslint-config-standard';
 import deprecationPlugin from 'eslint-plugin-deprecation';
 // @ts-expect-error No definition for this one
 import headerPlugin from 'eslint-plugin-header';
-// @ts-expect-error No definition for this one
 import importPlugin from 'eslint-plugin-import';
 // @ts-expect-error No definition for this one
 import importNewlinesPlugin from 'eslint-plugin-import-newlines';
@@ -20,7 +19,6 @@ import jestPlugin from 'eslint-plugin-jest';
 import nPlugin from 'eslint-plugin-n';
 // @ts-expect-error No definition for this one
 import promisePlugin from 'eslint-plugin-promise';
-// @ts-expect-error No definition for this one
 import reactPlugin from 'eslint-plugin-react';
 // @ts-expect-error No definition for this one
 import reactHooksPlugin from 'eslint-plugin-react-hooks';
diff --git a/packages/dev/config/tsconfig.json b/packages/dev/config/tsconfig.json
index e6f320c..5ff939e 100644
--- a/packages/dev/config/tsconfig.json
+++ b/packages/dev/config/tsconfig.json
@@ -5,6 +5,14 @@
    */
   "extends": "@tsconfig/strictest/tsconfig.json",
   "compilerOptions": {
+    /**
+     * JavaScript sources are type-checked like the rest. The base set this
+     * until @tsconfig/strictest 2.0.8 dropped checkJs, which left every .js and
+     * .mjs file outside the program: lint could not parse them with type info.
+     */
+    "allowJs": true,
+    "checkJs": true,
+
     /**
      * Aligns with packages/dev/scripts/pezkuwi-dev-build-ts & packages/dev-ts/src/loader
      * (target here is specifically tied to the minimum supported Node version)