diff --git a/package.json b/package.json
index ad763f0bc2..c84a0164e2 100644
--- a/package.json
+++ b/package.json
@@ -39,7 +39,7 @@
     "ts-loader": "^4.5.0",
     "tslint": "^5.9.1",
     "tslint-consistent-codestyle": "^1.13.0",
-    "typescript": "3.0",
+    "typescript": "3.1",
     "vinyl-buffer": "^1.0.0",
     "vinyl-source-stream": "^1.1.0",
     "webpack": "^4.17.1",
diff --git a/src/shared/atlas/CharAtlasGenerator.ts b/src/shared/atlas/CharAtlasGenerator.ts
index f78a6d416c..60138d79f4 100644
--- a/src/shared/atlas/CharAtlasGenerator.ts
+++ b/src/shared/atlas/CharAtlasGenerator.ts
@@ -8,22 +8,13 @@ import { CHAR_ATLAS_CELL_SPACING, ICharAtlasConfig } from './Types';
 import { IColor } from '../Types';
 import { isFirefox, isSafari } from '../utils/Browser';
 
-declare const Promise: any;
-
-export interface IOffscreenCanvas {
-  width: number;
-  height: number;
-  getContext(type: '2d', config?: Canvas2DContextAttributes): CanvasRenderingContext2D;
-  transferToImageBitmap(): ImageBitmap;
-}
-
 /**
  * Generates a char atlas.
  * @param context The window or worker context.
  * @param canvasFactory A function to generate a canvas with a width or height.
  * @param config The config for the new char atlas.
  */
-export function generateStaticCharAtlasTexture(context: Window, canvasFactory: (width: number, height: number) => HTMLCanvasElement | IOffscreenCanvas, config: ICharAtlasConfig): HTMLCanvasElement | Promise<ImageBitmap> {
+export function generateStaticCharAtlasTexture(context: Window, canvasFactory: (width: number, height: number) => HTMLCanvasElement, config: ICharAtlasConfig): HTMLCanvasElement | Promise<ImageBitmap> {
   const cellWidth = config.scaledCharWidth + CHAR_ATLAS_CELL_SPACING;
   const cellHeight = config.scaledCharHeight + CHAR_ATLAS_CELL_SPACING;
   const canvas = canvasFactory(
@@ -101,12 +92,7 @@ export function generateStaticCharAtlasTexture(context: Window, canvasFactory: (
   // performance (tested on v55).
   if (!('createImageBitmap' in context) || isFirefox || isSafari) {
     // Don't attempt to clear background colors if createImageBitmap is not supported
-    if (canvas instanceof HTMLCanvasElement) {
-      // Just return the HTMLCanvas if it's a HTMLCanvasElement
-      return canvas;
-    }
-    // Transfer to an ImageBitmap is this is an OffscreenCanvas
-    return new Promise((r: (bitmap: ImageBitmap) => void) => r(canvas.transferToImageBitmap()));
+    return canvas;
   }
 
   const charAtlasImageData = ctx.getImageData(0, 0, canvas.width, canvas.height);
diff --git a/src/ui/ScreenDprMonitor.ts b/src/ui/ScreenDprMonitor.ts
index 9247a0329d..d66eeb64f3 100644
--- a/src/ui/ScreenDprMonitor.ts
+++ b/src/ui/ScreenDprMonitor.ts
@@ -19,7 +19,7 @@ export type ScreenDprListener = (newDevicePixelRatio?: number, oldDevicePixelRat
  */
 export class ScreenDprMonitor extends Disposable {
   private _currentDevicePixelRatio: number;
-  private _outerListener: MediaQueryListListener;
+  private _outerListener: (this: MediaQueryList, ev: MediaQueryListEvent) => any;
   private _listener: ScreenDprListener;
   private _resolutionMediaMatchList: MediaQueryList;
 
diff --git a/yarn.lock b/yarn.lock
index 267c3bfccb..db31bfe17a 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -6716,10 +6716,10 @@ typedarray@^0.0.6, typedarray@~0.0.5:
   resolved "https://registry.yarnpkg.com/typedarray/-/typedarray-0.0.6.tgz#867ac74e3864187b1d3d47d996a78ec5c8830777"
   integrity sha1-hnrHTjhkGHsdPUfZlqeOxciDB3c=
 
-typescript@3.0:
-  version "3.0.3"
-  resolved "https://registry.yarnpkg.com/typescript/-/typescript-3.0.3.tgz#4853b3e275ecdaa27f78fda46dc273a7eb7fc1c8"
-  integrity sha512-kk80vLW9iGtjMnIv11qyxLqZm20UklzuR2tL0QAnDIygIUIemcZMxlMWudl9OOt76H3ntVzcTiddQ1/pAAJMYg==
+typescript@3.1:
+  version "3.1.6"
+  resolved "https://registry.yarnpkg.com/typescript/-/typescript-3.1.6.tgz#b6543a83cfc8c2befb3f4c8fba6896f5b0c9be68"
+  integrity sha512-tDMYfVtvpb96msS1lDX9MEdHrW4yOuZ4Kdc4Him9oU796XldPYF/t2+uKoX0BBa0hXXwDlqYQbXY5Rzjzc5hBA==
 
 uglify-es@^3.3.4:
   version "3.3.9"