diff --git a/src/api-demo-base.ts b/src/api-demo-base.ts
index 984ca43..5550caf 100644
--- a/src/api-demo-base.ts
+++ b/src/api-demo-base.ts
@@ -39,7 +39,7 @@ export class ApiDemoBase extends ApiViewerMixin(LitElement) {
     this._id = id++;
   }
 
-  protected render() {
+  protected render(): TemplateResult {
     return html`
       ${until(
         renderDemo(this.jsonFetched, this.selected, this._id, this.excludeKnobs)
diff --git a/src/api-demo-content.ts b/src/api-demo-content.ts
index e69475d..f330eb8 100644
--- a/src/api-demo-content.ts
+++ b/src/api-demo-content.ts
@@ -1,4 +1,10 @@
-import { LitElement, html, customElement, property } from 'lit-element';
+import {
+  LitElement,
+  html,
+  customElement,
+  property,
+  TemplateResult
+} from 'lit-element';
 import { ElementInfo } from './lib/types.js';
 import { EMPTY_ELEMENT } from './lib/constants.js';
 import './api-viewer-demo.js';
@@ -17,7 +23,7 @@ export class ApiDemoContent extends LitElement {
     return this;
   }
 
-  protected render() {
+  protected render(): TemplateResult {
     const { elements, selected, exclude, vid } = this;
 
     const { name, properties, slots, events, cssProperties } = {
diff --git a/src/api-docs-base.ts b/src/api-docs-base.ts
index 59766ee..6d4faef 100644
--- a/src/api-docs-base.ts
+++ b/src/api-docs-base.ts
@@ -23,7 +23,7 @@ async function renderDocs(
 }
 
 export class ApiDocsBase extends ApiViewerMixin(LitElement) {
-  protected render() {
+  protected render(): TemplateResult {
     return html`${until(renderDocs(this.jsonFetched, this.selected))}`;
   }
 }
diff --git a/src/api-docs-content.ts b/src/api-docs-content.ts
index b71e0df..59c1841 100644
--- a/src/api-docs-content.ts
+++ b/src/api-docs-content.ts
@@ -1,4 +1,10 @@
-import { LitElement, html, customElement, property } from 'lit-element';
+import {
+  LitElement,
+  html,
+  customElement,
+  property,
+  TemplateResult
+} from 'lit-element';
 import { ElementInfo } from './lib/types.js';
 import { EMPTY_ELEMENT } from './lib/constants.js';
 import { parse } from './lib/markdown.js';
@@ -14,7 +20,7 @@ export class ApiDocsContent extends LitElement {
     return this;
   }
 
-  protected render() {
+  protected render(): TemplateResult {
     const { elements, selected } = this;
 
     const {
diff --git a/src/api-viewer-base.ts b/src/api-viewer-base.ts
index 0381133..6be3842 100644
--- a/src/api-viewer-base.ts
+++ b/src/api-viewer-base.ts
@@ -44,7 +44,7 @@ export class ApiViewerBase extends ApiViewerMixin(LitElement) {
     this._id = id++;
   }
 
-  protected render() {
+  protected render(): TemplateResult {
     return html`
       ${until(
         renderDocs(
diff --git a/src/api-viewer-content.ts b/src/api-viewer-content.ts
index ff4e4e4..8f1f17f 100644
--- a/src/api-viewer-content.ts
+++ b/src/api-viewer-content.ts
@@ -1,4 +1,10 @@
-import { LitElement, html, customElement, property } from 'lit-element';
+import {
+  LitElement,
+  html,
+  customElement,
+  property,
+  TemplateResult
+} from 'lit-element';
 import { cache } from 'lit-html/directives/cache.js';
 import { ElementInfo } from './lib/types.js';
 import { EMPTY_ELEMENT } from './lib/constants.js';
@@ -18,11 +24,11 @@ export class ApiViewerContent extends LitElement {
 
   @property({ type: Number }) vid?: number;
 
-  protected createRenderRoot() {
+  protected createRenderRoot(): this {
     return this;
   }
 
-  protected render() {
+  protected render(): TemplateResult {
     const { elements, selected, section, exclude, vid } = this;
 
     const {
diff --git a/src/api-viewer-demo-events.ts b/src/api-viewer-demo-events.ts
index 73c248a..664ef84 100644
--- a/src/api-viewer-demo-events.ts
+++ b/src/api-viewer-demo-events.ts
@@ -43,7 +43,7 @@ export class ApiViewerDemoEvents extends LitElement {
     return this;
   }
 
-  protected render() {
+  protected render(): TemplateResult {
     const { log } = this;
     return html`
       <button
diff --git a/src/api-viewer-demo-layout.ts b/src/api-viewer-demo-layout.ts
index f417c3a..a3e8a9c 100644
--- a/src/api-viewer-demo-layout.ts
+++ b/src/api-viewer-demo-layout.ts
@@ -1,4 +1,10 @@
-import { LitElement, html, customElement, property } from 'lit-element';
+import {
+  LitElement,
+  html,
+  customElement,
+  property,
+  TemplateResult
+} from 'lit-element';
 import { renderer } from './lib/renderer.js';
 import {
   cssPropRenderer,
@@ -22,7 +28,7 @@ export class ApiViewerDemoLayout extends ApiDemoLayoutMixin(LitElement) {
     return this;
   }
 
-  protected render() {
+  protected render(): TemplateResult {
     const [noCss, noEvents, noSlots, noCustomKnobs, noProps] = [
       this.cssProps,
       this.events,
diff --git a/src/api-viewer-demo-snippet.ts b/src/api-viewer-demo-snippet.ts
index 264fc2b..6296c19 100644
--- a/src/api-viewer-demo-snippet.ts
+++ b/src/api-viewer-demo-snippet.ts
@@ -175,7 +175,7 @@ export class ApiViewerDemoSnippet extends LitElement {
     ];
   }
 
-  protected render() {
+  protected render(): TemplateResult {
     return html`
       ${renderSnippet(
         this.vid as number,
diff --git a/src/api-viewer-demo.ts b/src/api-viewer-demo.ts
index fc9f929..b14001e 100644
--- a/src/api-viewer-demo.ts
+++ b/src/api-viewer-demo.ts
@@ -61,7 +61,7 @@ export class ApiViewerDemo extends LitElement {
     return this;
   }
 
-  protected render() {
+  protected render(): TemplateResult {
     const { name } = this;
 
     if (name && this.lastName !== name) {
diff --git a/src/api-viewer-docs.ts b/src/api-viewer-docs.ts
index 4bcf021..b094089 100644
--- a/src/api-viewer-docs.ts
+++ b/src/api-viewer-docs.ts
@@ -112,7 +112,7 @@ export class ApiViewerDocs extends LitElement {
     return this;
   }
 
-  protected render() {
+  protected render(): TemplateResult {
     const { slots, props, attrs, events, cssParts, cssProps } = this;
 
     const properties = props || [];
diff --git a/src/api-viewer-panel.ts b/src/api-viewer-panel.ts
index 716f603..9e9e49d 100644
--- a/src/api-viewer-panel.ts
+++ b/src/api-viewer-panel.ts
@@ -1,4 +1,10 @@
-import { LitElement, html, customElement, css } from 'lit-element';
+import {
+  LitElement,
+  html,
+  customElement,
+  css,
+  TemplateResult
+} from 'lit-element';
 
 let panelIdCounter = 0;
 
@@ -19,7 +25,7 @@ export class ApiViewerPanel extends LitElement {
     `;
   }
 
-  protected render() {
+  protected render(): TemplateResult {
     return html`<slot></slot>`;
   }
 
diff --git a/src/api-viewer-tab.ts b/src/api-viewer-tab.ts
index 8e45332..60d9ca5 100644
--- a/src/api-viewer-tab.ts
+++ b/src/api-viewer-tab.ts
@@ -4,7 +4,8 @@ import {
   customElement,
   css,
   property,
-  PropertyValues
+  PropertyValues,
+  TemplateResult
 } from 'lit-element';
 
 let tabIdCounter = 0;
@@ -107,7 +108,7 @@ export class ApiViewerTab extends LitElement {
     `;
   }
 
-  protected render() {
+  protected render(): TemplateResult {
     return html`${this.heading}`;
   }
 
diff --git a/src/fixtures/fancy-accordion.ts b/src/fixtures/fancy-accordion.ts
index d2c45eb..9a682f3 100644
--- a/src/fixtures/fancy-accordion.ts
+++ b/src/fixtures/fancy-accordion.ts
@@ -4,7 +4,8 @@ import {
   css,
   customElement,
   property,
-  PropertyValues
+  PropertyValues,
+  TemplateResult
 } from 'lit-element';
 import { ExpansionPanel } from './expansion-panel.js';
 
@@ -75,7 +76,7 @@ export class FancyAccordion extends LitElement {
     `;
   }
 
-  protected render() {
+  protected render(): TemplateResult {
     return html`<slot></slot>`;
   }
 
diff --git a/src/fixtures/intl-currency.ts b/src/fixtures/intl-currency.ts
index 2e33222..967f09f 100644
--- a/src/fixtures/intl-currency.ts
+++ b/src/fixtures/intl-currency.ts
@@ -1,4 +1,11 @@
-import { LitElement, html, css, customElement, property } from 'lit-element';
+import {
+  LitElement,
+  html,
+  css,
+  customElement,
+  property,
+  TemplateResult
+} from 'lit-element';
 
 const format = (
   value: number,
@@ -49,7 +56,7 @@ export class IntlCurrency extends LitElement {
     `;
   }
 
-  protected render() {
+  protected render(): TemplateResult {
     return html`
       <div part="value">${format(this.value, this.currency, this.locale)}</div>
     `;
diff --git a/src/fixtures/progress-bar.ts b/src/fixtures/progress-bar.ts
index 3798a3f..3c9ab05 100644
--- a/src/fixtures/progress-bar.ts
+++ b/src/fixtures/progress-bar.ts
@@ -4,7 +4,8 @@ import {
   css,
   customElement,
   property,
-  PropertyValues
+  PropertyValues,
+  TemplateResult
 } from 'lit-element';
 
 const normalizeValue = (value: number, min: number, max: number) => {
@@ -152,7 +153,7 @@ export class ProgressBar extends LitElement {
     `;
   }
 
-  protected render() {
+  protected render(): TemplateResult {
     return html`<div part="bar"><div part="value"></div></div>`;
   }