diff --git a/src/optimizer/src/rollup/index.ts b/src/optimizer/src/rollup/index.ts
index 17ca39f09e7..aa9c94afad4 100644
--- a/src/optimizer/src/rollup/index.ts
+++ b/src/optimizer/src/rollup/index.ts
@@ -56,7 +56,7 @@ export function qwikRollup(opts: QwikPluginOptions = {}): any {
       result = await optimizer.transformFs(transformOpts);
       result.modules.forEach((output) => {
         const path = output.path.split('.').slice(0, -1).join('.');
-        const key = transformOpts.rootDir + '/' + path;
+        const key = transformOpts.rootDir + optimizer.path.sep + path;
         transformedOutputs.set(key, output);
       });