Apple watch app, App store submission issue

I developed a companion apple watch app for our iOS app. I was able to successfully archive the build but I am getting this error mail from Appstore connect when submitting the build - 

ITMS-90562: Invalid Bundle - One of the nested bundles is built for a platform which is different from the main bundle platform. Please make sure that all bundles have correct platform specification.

Any idea how to fix this issue?