subtracting identical object values typescript

Question

I would to know how to subtract identical object values in typescript using Generics and type-safe, based on: subtracting identical object values javascript

    const subtractObjects = <T extends Record<String, number>>(objA: T, objB: T): T =>
      Object.keys(objA).reduce((a, k) => {
        a[k] = objA[k] - objB[k];
        return a;
      }, {});

I receive the error:

Type '{}' is not assignable to type 'T'.
  '{}' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint 'Record<string, number>'.