Error: No provider for Overlay!

I managed to eliminate this error by adding this to app.module.js:

import {OVERLAY_PROVIDERS} from "@angular/material";

@NgModule({
  imports: [...
  ],
  declarations: [...],
  providers: [OVERLAY_PROVIDERS],
  bootstrap: [...]
})

Edit (May 2018):

OVERLAY_PROVIDERS is now deprecated. use the OverlayModule instead

import { OverlayModule } from '@angular/cdk/overlay';

@NgModule({
  imports: [
      OverlayModule
  ],
  declarations: [...],
  providers: [...],
  bootstrap: [...]
})