diff --git a/lib/index.ts b/lib/index.ts
index cfae547d..958cb623 100644
--- a/lib/index.ts
+++ b/lib/index.ts
@@ -80,10 +80,6 @@ Object.assign(lookup, {
   connect: lookup,
 });
 
-if (typeof module !== "undefined") {
-  module.exports = lookup;
-}
-
 /**
  * Protocol version.
  *
diff --git a/postcompile.sh b/postcompile.sh
index 5c3aa390..e243e869 100755
--- a/postcompile.sh
+++ b/postcompile.sh
@@ -6,3 +6,6 @@ cp ./support/package.esm.json ./build/esm/package.json
 cp -r ./build/esm/ ./build/esm-debug/
 
 sed -i '/debug(/d' ./build/esm/*.js
+
+# for backward compatibility with `const socket = require("socket.io-client")(...)`
+echo -e '\nmodule.exports = lookup;' >> ./build/cjs/index.js