diff --git a/packages/core/cjsBuild.js b/packages/core/cjsBuild.js
new file mode 100644
index 0000000..f4e0427
--- /dev/null
+++ b/packages/core/cjsBuild.js
@@ -0,0 +1,33 @@
+const path = require("path")
+
+const isProd = process.argv[2] === "--prod"
+
+const fixCjsPlugin = {
+  name: "fixCJS",
+  setup(build) {
+    build.onResolve({ filter: /useSyncExternalStore/ }, (args) => {
+      return {
+        path: path.join(args.resolveDir, args.path + "Cjs.ts"),
+      }
+    })
+  },
+}
+
+require("esbuild")
+  .build({
+    entryPoints: ["src/index.tsx"],
+    bundle: true,
+    outfile: isProd
+      ? "./dist/core.cjs.production.min.js"
+      : "./dist/core.cjs.development.js",
+    target: "es2015",
+    minify: isProd,
+    external: ["react", "rxjs", "use-sync-external-store"],
+    format: "cjs",
+    sourcemap: true,
+    plugins: [fixCjsPlugin],
+  })
+  .catch((error) => {
+    console.error(error)
+    process.exit(1)
+  })
diff --git a/packages/core/package.json b/packages/core/package.json
index 99feab5..a649f07 100644
--- a/packages/core/package.json
+++ b/packages/core/package.json
@@ -27,8 +27,8 @@
     "build": "yarn build:ts && yarn build:esm2017 && yarn build:esm2019 && yarn build:cjs:dev && yarn build:cjs:prod",
     "build:esm2019": "esbuild src/index.tsx --bundle --outfile=./dist/core.es2019.mjs --target=es2019 --external:react --external:rxjs --external:use-sync-external-store --format=esm --sourcemap",
     "build:esm2017": "esbuild src/index.tsx --bundle --outfile=./dist/core.es2017.js --target=es2017 --external:react --external:rxjs --external:use-sync-external-store --format=esm --sourcemap",
-    "build:cjs:dev": "esbuild src/index.tsx --bundle --outfile=./dist/core.cjs.development.js --target=es2015 --external:react --external:rxjs --external:use-sync-external-store --format=cjs --sourcemap",
-    "build:cjs:prod": "esbuild src/index.tsx --bundle --outfile=./dist/core.cjs.production.min.js --target=es2015 --external:react --external:rxjs --external:use-sync-external-store  --format=cjs --minify --sourcemap",
+    "build:cjs:dev": "node cjsBuild.js",
+    "build:cjs:prod": "node cjsBuild.js --prod",
     "build:ts": "tsc -p ./tsconfig-build.json --outDir ./dist --skipLibCheck --emitDeclarationOnly",
     "test": "jest --coverage",
     "lint": "prettier --check README.md \"src/**/*.{js,jsx,ts,tsx,json,md}\"",
diff --git a/packages/core/src/internal/useObservable.ts b/packages/core/src/internal/useObservable.ts
index e9a0794..bdb1e66 100644
--- a/packages/core/src/internal/useObservable.ts
+++ b/packages/core/src/internal/useObservable.ts
@@ -1,9 +1,9 @@
 import { Subscription } from "rxjs"
-import { useSyncExternalStore } from "use-sync-external-store/shim/index.js"
 import { useRef, useState } from "react"
 import { SUSPENSE, filterOutSuspense } from "../SUSPENSE"
 import { DefaultedStateObservable, StateObservable } from "@josepot/rxjs-state"
 import { EMPTY_VALUE } from "./empty-value"
+import useSyncExternalStore from "./useSyncExternalStore"
 
 type VoidCb = () => void
 
diff --git a/packages/core/src/internal/useSyncExternalStore.ts b/packages/core/src/internal/useSyncExternalStore.ts
new file mode 100644
index 0000000..38f041f
--- /dev/null
+++ b/packages/core/src/internal/useSyncExternalStore.ts
@@ -0,0 +1 @@
+export { useSyncExternalStore as default } from "use-sync-external-store/shim/index.js"
diff --git a/packages/core/src/internal/useSyncExternalStoreCjs.ts b/packages/core/src/internal/useSyncExternalStoreCjs.ts
new file mode 100644
index 0000000..65ca0cd
--- /dev/null
+++ b/packages/core/src/internal/useSyncExternalStoreCjs.ts
@@ -0,0 +1 @@
+export { useSyncExternalStore as default } from "use-sync-external-store/shim"