diff --git a/aio/src/app/custom-elements/api/api-list.component.html b/aio/src/app/custom-elements/api/api-list.component.html
index 7e0eb0f0fd..cd3aeafb19 100644
--- a/aio/src/app/custom-elements/api/api-list.component.html
+++ b/aio/src/app/custom-elements/api/api-list.component.html
@@ -21,9 +21,9 @@
 </div>
 
 <article class="api-list-container l-content-small docs-content">
-  <div *ngFor="let section of filteredSections | async" >
+  <div *ngFor="let section of (filteredSections | async)!" >
     <h2 *ngIf="section.items"><a [href]="section.path" [class.deprecated-api-item]="section.deprecated">{{section.title}}</a></h2>
-    <ul class="api-list" *ngIf="section.items?.length">
+    <ul class="api-list" *ngIf="section.items && section.items.length">
       <ng-container *ngFor="let item of section.items">
         <li class="api-item">
           <a [href]="item.path" [class.deprecated-api-item]="item.stability === 'deprecated'">
diff --git a/aio/src/app/custom-elements/code/code-tabs.component.ts b/aio/src/app/custom-elements/code/code-tabs.component.ts
index 7067788db5..3a507f2b64 100644
--- a/aio/src/app/custom-elements/code/code-tabs.component.ts
+++ b/aio/src/app/custom-elements/code/code-tabs.component.ts
@@ -3,13 +3,14 @@ import { AfterViewInit, Component, ElementRef, Input, OnInit, QueryList, ViewChi
 import { CodeComponent } from './code.component';
 
 export interface TabInfo {
-  class: string|null;
+  class: string;
   code: string;
-  language: string|null;
-  linenums: any;
   path: string;
   region: string;
-  header: string|null;
+
+  header?: string;
+  language?: string;
+  linenums?: string;
 }
 
 /**
@@ -46,7 +47,7 @@ export interface TabInfo {
 export class CodeTabsComponent implements OnInit, AfterViewInit {
   tabs: TabInfo[];
 
-  @Input() linenums: string;
+  @Input() linenums: string | undefined;
 
   @ViewChild('content', { static: true }) content: ElementRef<HTMLDivElement>;
 
@@ -70,13 +71,14 @@ export class CodeTabsComponent implements OnInit, AfterViewInit {
   /** Gets the extracted TabInfo data from the provided code-pane element. */
   private getTabInfo(tabContent: Element): TabInfo {
     return {
-      class: tabContent.getAttribute('class'),
+      class: tabContent.getAttribute('class') || '',
       code: tabContent.innerHTML,
-      language: tabContent.getAttribute('language'),
-      linenums: tabContent.getAttribute('linenums') || this.linenums,
       path: tabContent.getAttribute('path') || '',
       region: tabContent.getAttribute('region') || '',
-      header: tabContent.getAttribute('header')
+
+      header: tabContent.getAttribute('header') || undefined,
+      language: tabContent.getAttribute('language') || undefined,
+      linenums: tabContent.getAttribute('linenums') || this.linenums,
     };
   }
 }
diff --git a/aio/src/app/custom-elements/toc/toc.component.ts b/aio/src/app/custom-elements/toc/toc.component.ts
index dce71b3493..0cbab775b6 100644
--- a/aio/src/app/custom-elements/toc/toc.component.ts
+++ b/aio/src/app/custom-elements/toc/toc.component.ts
@@ -20,7 +20,7 @@ export class TocComponent implements OnInit, AfterViewInit, OnDestroy {
   isEmbedded = false;
   @ViewChildren('tocItem') private items: QueryList<ElementRef>;
   private onDestroy = new Subject();
-  private primaryMax = 4;
+  primaryMax = 4;
   tocList: TocItem[];
 
   constructor(
diff --git a/aio/src/app/navigation/navigation.model.ts b/aio/src/app/navigation/navigation.model.ts
index e54f175977..1d832de471 100644
--- a/aio/src/app/navigation/navigation.model.ts
+++ b/aio/src/app/navigation/navigation.model.ts
@@ -3,8 +3,13 @@
 // Then re-export them from `navigation.service.ts`
 
 export interface NavigationNode {
+  // NOTE:
+  // A navigation node should always have a title (to display to the user).
+  // It may also have `url` (if it is a leaf node) or `children` (and no `url`), but it should
+  // always have `title`.
+  title: string;
+
   url?: string;
-  title?: string;
   tooltip?: string;
   hidden?: boolean;
   children?: NavigationNode[];
diff --git a/aio/src/app/navigation/navigation.service.spec.ts b/aio/src/app/navigation/navigation.service.spec.ts
index 0fe14590c7..541ec5bd14 100644
--- a/aio/src/app/navigation/navigation.service.spec.ts
+++ b/aio/src/app/navigation/navigation.service.spec.ts
@@ -41,8 +41,8 @@ describe('NavigationService', () => {
       navService.navigationViews.subscribe(views => viewsEvents.push(views));
 
       expect(viewsEvents).toEqual([]);
-      httpMock.expectOne({}).flush({ TopBar: [ { url: 'a' }] });
-      expect(viewsEvents).toEqual([{ TopBar: [ { url: 'a' }] }]);
+      httpMock.expectOne({}).flush({ TopBar: [ { title: '', url: 'a' }] });
+      expect(viewsEvents).toEqual([{ TopBar: [ { title: '', url: 'a' }] }]);
     });
 
     it('navigationViews observable should complete', () => {
@@ -82,7 +82,7 @@ describe('NavigationService', () => {
       { title: 'a', tooltip: 'a tip' },
       { title: 'b' },
       { title: 'c!'},
-      { url: 'foo' }
+      { title: '', url: 'foo' }
     ];
 
     beforeEach(() => {
diff --git a/aio/src/app/shared/search-results/search-results.component.ts b/aio/src/app/shared/search-results/search-results.component.ts
index 9e684c9dba..79efb76e34 100644
--- a/aio/src/app/shared/search-results/search-results.component.ts
+++ b/aio/src/app/shared/search-results/search-results.component.ts
@@ -14,7 +14,7 @@ export class SearchResultsComponent implements OnChanges {
    * The results to display
    */
   @Input()
-  searchResults: SearchResults;
+  searchResults: SearchResults | null = null;
 
   /**
    * Emitted when the user selects a search result
@@ -39,7 +39,7 @@ export class SearchResultsComponent implements OnChanges {
   }
 
   // Map the search results into groups by area
-  private processSearchResults(search: SearchResults) {
+  private processSearchResults(search: SearchResults | null) {
     if (!search) {
       return [];
     }
diff --git a/aio/tsconfig.json b/aio/tsconfig.json
index d7427181d1..aed6d03332 100644
--- a/aio/tsconfig.json
+++ b/aio/tsconfig.json
@@ -37,8 +37,7 @@
   ],
   "angularCompilerOptions": {
     "disableTypeScriptVersionCheck": true,
-    // TODO: Fix template type errors and enable.
-    // "fullTemplateTypeCheck": true,
+    "fullTemplateTypeCheck": true,
     "strictInjectionParameters": true
   }
 }