diff --git a/.eslintrc.cjs b/.eslintrc.cjs
index ae7644b57..79a36054f 100644
--- a/.eslintrc.cjs
+++ b/.eslintrc.cjs
@@ -76,6 +76,16 @@ module.exports = {
         project: ['./tsconfig.packages.json'],
       },
       rules: {
+        '@typescript-eslint/explicit-function-return-type': [
+          'error',
+          {
+            // To permit omitting the return type in situations like:
+            // `const obj = { foo: (bar: string) => bar };`
+            // We'll presume that `obj` has a type that enforces the return type.
+            allowExpressions: true,
+          },
+        ],
+
         '@typescript-eslint/no-explicit-any': 'error',
 
         // This rule is broken, and without the `allowAny` option, it reports a lot
diff --git a/packages/shims/src/vitest-environment-endoified.ts b/packages/shims/src/vitest-environment-endoified.ts
index 63a817387..1f0131bc6 100644
--- a/packages/shims/src/vitest-environment-endoified.ts
+++ b/packages/shims/src/vitest-environment-endoified.ts
@@ -13,8 +13,9 @@ export default {
           clearTimeout,
         });
       },
-      // eslint-disable-next-line no-empty-function
-      teardown(): void {},
+      teardown(): void {
+        return undefined;
+      },
     };
   },
   async setup() {