pulumi: TypeError: pulumi.runtime.registerResourceModule is not a function

I’ve just updated to version 2.15.6 from 2.15.0 of pulumi and started seeing this issue when previewing deployments.

TypeError: pulumi.runtime.registerResourceModule is not a function

Full Output:

    error: Running program '/infra' failed with an unhandled exception:
    TypeError: pulumi.runtime.registerResourceModule is not a function
        at Object.<anonymous> (/infra/node_modules/@pulumi/index.ts:49:16)
        at Module._compile (node:internal/modules/cjs/loader:1102:14)
        at Object.Module._extensions..js (node:internal/modules/cjs/loader:1131:10)
        at Module.load (node:internal/modules/cjs/loader:967:32)
        at Function.Module._load (node:internal/modules/cjs/loader:807:14)
        at Module.require (node:internal/modules/cjs/loader:991:19)
        at require (node:internal/modules/cjs/helpers:92:18)
        at Object.<anonymous> (/infra/config/postgresql.ts:3:1)
        at Module._compile (node:internal/modules/cjs/loader:1102:14)
        at Module.m._compile (//infra/node_modules/ts-node/src/index.ts:439:23)

Expected Behavior

Preview / Up commands work prroperly.

Current Behavior

Error during previews

TypeError: pulumi.runtime.registerResourceModule is not a function

Steps to Reproduce

Context (Environment)

MAC OS - Big Sur.

Pulumi 2.15.6