diff --git a/package.json b/package.json
index b8f18ff..e7472b5 100644
--- a/package.json
+++ b/package.json
@@ -22,19 +22,23 @@
   "exports": {
     ".": {
       "types": "./dist/index.d.ts",
-      "import": "./dist/index.js"
+      "import": "./dist/index.js",
+      "default": "./dist/index.js"
     },
     "./react": {
       "types": "./dist/react/index.d.ts",
-      "import": "./dist/react/index.js"
+      "import": "./dist/react/index.js",
+      "default": "./dist/react/index.js"
     },
     "./solid": {
       "types": "./dist/solid/index.d.ts",
-      "import": "./dist/solid/index.js"
+      "import": "./dist/solid/index.js",
+      "default": "./dist/solid/index.js"
     },
     "./internal": {
       "types": "./dist/internal.d.ts",
-      "import": "./dist/internal.js"
+      "import": "./dist/internal.js",
+      "default": "./dist/internal.js"
     }
   },
   "files": [
diff --git a/scripts/check-bundle.mjs b/scripts/check-bundle.mjs
index 8c9562a..9cd51e6 100644
--- a/scripts/check-bundle.mjs
+++ b/scripts/check-bundle.mjs
@@ -6,6 +6,7 @@
  *   npm run build && node scripts/check-bundle.mjs
  */
 import { readFileSync, readdirSync } from 'node:fs';
+import { createRequire } from 'node:module';
 import { join } from 'node:path';
 
 const DIST = 'dist';
@@ -148,6 +149,24 @@ for (const [file, peer] of [
   );
 }
 
+// Every entry must resolve for a CommonJS consumer too: the `default` condition
+// is what a `require()` resolver matches, and Node ≥ 20.19 (the engines floor)
+// loads the ESM file through it. Self-referencing by package name goes through
+// the same exports map a consumer sees.
+const require = createRequire(import.meta.url);
+for (const subpath of ['apecs', 'apecs/react', 'apecs/solid', 'apecs/internal']) {
+  try {
+    require.resolve(subpath);
+  } catch (error) {
+    check(false, `${subpath} does not resolve for require(): ${error.code ?? error.message}`);
+  }
+}
+try {
+  check(typeof require('apecs').VERSION === 'string', 'require("apecs") does not load the entry');
+} catch (error) {
+  check(false, `require("apecs") throws: ${error.code ?? error.message}`);
+}
+
 if (failures.length > 0) {
   for (const failure of failures) {
     console.error(`✗ ${failure}`);