diff --git a/babel.config.js b/babel.config.cjs
similarity index 100%
rename from babel.config.js
rename to babel.config.cjs
diff --git a/scripts/switch_package_to_release.js b/scripts/switch_package_to_release.js
index 2ef9bb09cb2..353840d4d92 100755
--- a/scripts/switch_package_to_release.js
+++ b/scripts/switch_package_to_release.js
@@ -11,6 +11,11 @@ async function main() {
             pkgJson[field] = pkgJson["matrix_lib_" + field];
         }
     }
+
+    // matrix-js-sdk is built into ECMAScript modules. Make sure we declare it as such.
+    // See https://nodejs.org/api/packages.html#type.
+    pkgJson["type"] = "module";
+
     await fsProm.writeFile(PKGJSON, JSON.stringify(pkgJson, null, 2));
 }