diff --git a/packages/osd-optimizer/src/worker/webpack.config.ts b/packages/osd-optimizer/src/worker/webpack.config.ts
index 6adfc1d6d90a..cfe79b4b19a1 100644
--- a/packages/osd-optimizer/src/worker/webpack.config.ts
+++ b/packages/osd-optimizer/src/worker/webpack.config.ts
@@ -235,6 +235,21 @@ export function getWebpackConfig(bundle: Bundle, bundleRefs: BundleRefs, worker:
             },
           },
         },
+        {
+          test: /\.js$/,
+          /* reactflow and some of its dependencies don't have es5 builds
+           * so we need to build from source and transpile for webpack v4
+           */
+          include: /node_modules[\\/]@?reactflow/,
+          use: {
+            loader: 'babel-loader',
+            options: {
+              babelrc: false,
+              envName: worker.dist ? 'production' : 'development',
+              presets: [BABEL_PRESET_PATH],
+            },
+          },
+        },
         {
           test: /\.(html|md|txt|tmpl)$/,
           use: {