diff --git a/tsdx.base.js b/tsdx.base.js
index 055339868..bdadae211 100644
--- a/tsdx.base.js
+++ b/tsdx.base.js
@@ -18,6 +18,10 @@ exports.createRollupConfig = (
     } else if (plugin.name === 'commonjs') {
       return commonjs({
         include: /\/node_modules\//,
+
+        // https://github.com/rollup/plugins/issues/304#issuecomment-619858916
+        // exclude: ['node_modules/symbol-observable/es/*.js'],
+
         ...swPlugins[plugin.name],
       })
     } else if (plugin.name in swPlugins) {
@@ -35,5 +39,9 @@ exports.createRollupConfig = (
     return external(id)
   }
 
+  if (config.output.format === 'umd') {
+    delete config.external
+  }
+
   return config
 }