diff --git a/.size-snapshot.json b/.size-snapshot.json
index 93e3cc8f..3a96a8a2 100644
--- a/.size-snapshot.json
+++ b/.size-snapshot.json
@@ -81,8 +81,8 @@
     "gzipped": 9217
   },
   "dist/rbx.umd.js": {
-    "bundled": 89389,
-    "minified": 45120,
-    "gzipped": 9269
+    "bundled": 89398,
+    "minified": 45131,
+    "gzipped": 9273
   }
 }
diff --git a/src/__tests__/testing.tsx b/src/__tests__/testing.tsx
index 07b8e092..1edf8ffa 100644
--- a/src/__tests__/testing.tsx
+++ b/src/__tests__/testing.tsx
@@ -18,22 +18,26 @@ export const contextManager = <
   TState extends object
 >(
   enter: (params: TParams) => { context: TContext; state: TState },
-  exit: (
-    {
-      context,
-      params,
-      state,
-    }: { context: TContext; params: TParams; state: TState },
-  ) => void,
+  exit: ({
+    context,
+    params,
+    state,
+  }: {
+    context: TContext;
+    params: TParams;
+    state: TState;
+  }) => void,
 ) => (
   params: TParams,
-  inner: (
-    {
-      context,
-      params,
-      state,
-    }: { context: TContext; params: TParams; state: TState },
-  ) => void,
+  inner: ({
+    context,
+    params,
+    state,
+  }: {
+    context: TContext;
+    params: TParams;
+    state: TState;
+  }) => void,
 ) => {
   const { context, state } = enter(params);
   try {
@@ -48,7 +52,10 @@ export const withWindow = contextManager(
   ({ value }: { value?: undefined } = {}) => {
     const window = (global as any).window;
     delete (global as any).window;
-    (global as any).window = value;
+
+    if (value !== undefined) {
+      (global as any).window = value;
+    }
 
     return { context: {}, state: { window } };
   },
diff --git a/src/__tests__/utils.test.ts b/src/__tests__/utils.test.ts
index 72325df8..5a464beb 100644
--- a/src/__tests__/utils.test.ts
+++ b/src/__tests__/utils.test.ts
@@ -14,8 +14,11 @@ describe("Utils", () => {
       expect(canUseDOM()).toBe(true);
     });
 
-    it("should return false without window", () => {
+    it("should return false without window (SSR)", () => {
       withWindow({}, () => {
+        expect(() => window).toThrow(
+          new ReferenceError("window is not defined"),
+        );
         expect(canUseDOM()).toBe(false);
       });
     });
diff --git a/src/utils.ts b/src/utils.ts
index 3857bab1..33d828cd 100644
--- a/src/utils.ts
+++ b/src/utils.ts
@@ -4,7 +4,7 @@ import { Lit } from "./types";
 
 export const canUseDOM = () =>
   !(
-    window === undefined ||
+    typeof window === "undefined" || // tslint:disable-line:no-typeof-undefined
     window.document === undefined ||
     window.document.createElement === undefined
   );