Module not found: Error: Can't resolve for file:// packages

[spacem]

I have a monorepo and in package.json have a local dependancy eg.
"core": "file:../core",

I get this error:

ERROR in ./sample-function/index.js
Module not found: Error: Can't resolve 'core' in 'C:\work\testing\functions\sample-function'
 @ ./sample-function/index.js 2:13-31
 @ ./.funcpack/index.gen.js(node:26204) UnhandledPromiseRejectionWarning: Error: Could not webpack project
    at Command.<anonymous> (C:\work\testing\functions\node_modules\azure-functions-pack\lib\main.js:158:19)
    at Generator.throw (<anonymous>)
    at rejected (C:\work\testing\functions\node_modules\azure-functions-pack\lib\main.js:6:65)
    at <anonymous>

I guess this comes from webpack? Any advice how to get past this?