diff --git a/lib/core/shell/README.md b/lib/core/shell/README.md
index 1ec3c83f4b6..332ae311dff 100644
--- a/lib/core/shell/README.md
+++ b/lib/core/shell/README.md
@@ -10,7 +10,8 @@ I order to attach routes to appShell, `withRoutes(routes: Routes | AppShellRoute
 
 Passed routes are going to be attached to [shell main route](./src/lib/shell.routes.ts)
 
-If you would like to provide custom app guard, you can provide your own using [SHELL_AUTH_TOKEN](./src/lib/shell.routes.ts)
+If you would like to provide custom app guard, you can provide your own using [SHELL_AUTH_TOKEN](./src/lib/shell.routes.ts). Keep in mind that
+the custom app guard must be a functional route guard, instead of a class based one. 
 
 ## Shell Service
 
diff --git a/lib/core/shell/src/lib/services/shell-app.service.ts b/lib/core/shell/src/lib/services/shell-app.service.ts
index a02d6a5c755..264d3f5fde3 100644
--- a/lib/core/shell/src/lib/services/shell-app.service.ts
+++ b/lib/core/shell/src/lib/services/shell-app.service.ts
@@ -16,23 +16,23 @@
  */
 
 import { InjectionToken } from '@angular/core';
-import { CanActivate, CanActivateChild } from '@angular/router';
+import { CanActivateFn, CanActivateChildFn } from '@angular/router';
 import { Observable } from 'rxjs';
 
 export interface ShellPreferencesService {
-  set(preferenceKey: string, value: any): void;
-  get(preferenceKey: string, defaultValue: string): string;
+    set(preferenceKey: string, value: any): void;
+    get(preferenceKey: string, defaultValue: string): string;
 }
 
 export interface ShellAppService {
-  pageHeading$: Observable<string>;
-  hideSidenavConditions: string[];
-  minimizeSidenavConditions: string[];
-  preferencesService: ShellPreferencesService;
+    pageHeading$: Observable<string>;
+    hideSidenavConditions: string[];
+    minimizeSidenavConditions: string[];
+    preferencesService: ShellPreferencesService;
 }
 
 export const SHELL_APP_SERVICE = new InjectionToken<ShellAppService>('SHELL_APP_SERVICE');
 
-export const SHELL_AUTH_TOKEN = new InjectionToken<CanActivate & CanActivateChild>('SHELL_AUTH_TOKEN');
+export const SHELL_AUTH_TOKEN = new InjectionToken<CanActivateFn & CanActivateChildFn>('SHELL_AUTH_TOKEN');
 export const SHELL_NAVBAR_MIN_WIDTH = new InjectionToken<number>('SHELL_NAVBAR_MIN_WIDTH');
 export const SHELL_NAVBAR_MAX_WIDTH = new InjectionToken<number>('SHELL_NAVBAR_MAX_WIDTH');