Angular2 RC6: ‘ is not a known element’

I received this error when I imported Module A into Module B, and then tried to use a component from Module A in Module B.

The solution is to declare that component in the exports array.

@NgModule({
  declarations: [
    MyComponent
  ],
  exports: [
    MyComponent
  ]
})
export class ModuleA {}

@NgModule({
  imports: [
    ModuleA
  ]
})
export class ModuleB {}