webSocket module not found

I'm experimenting with web sockets and ran into an unexpected error:

error TS2307: Cannot find module 'wasp/server/webSocket' or its corresponding type declarations.

error TS2307: Cannot find module 'wasp/server/webSocket' or its corresponding type declarations.

As shown in the attached screen grab, the webSocket module is indeed missing. I've tried

wasp clean

wasp clean

to no avail. Running Wasp 0.16.3

webSocket module not found - Wasp