diff --git a/src/client/global.ts b/src/client/global.ts
index 9c48417..eaf1e1c 100644
--- a/src/client/global.ts
+++ b/src/client/global.ts
@@ -36,20 +36,22 @@ export function createGlobalProxy(
 				const win: Self = value.self;
 				// indexing into window gives you the contentWindow of the subframes for some reason
 				// you can't *set* it so this should always be the right value
-				if (SCRAMJETCLIENT in win) {
-					// then we've already hooked this frame and we can just send over its proxy
-					return win[SCRAMJETCLIENT].globalProxy;
-				} else {
-					// this can happen if it's an about:blank iframe that we've never gotten the chance to inject into
-					// just make a new client for it and inject
-					const newclient = new ScramjetClient(win);
-					newclient.hook();
+				if (win) {
+					if (SCRAMJETCLIENT in win) {
+						// then we've already hooked this frame and we can just send over its proxy
+						return win[SCRAMJETCLIENT].globalProxy;
+					} else {
+						// this can happen if it's an about:blank iframe that we've never gotten the chance to inject into
+						// just make a new client for it and inject
+						const newclient = new ScramjetClient(win);
+						newclient.hook();
 
-					return newclient.globalProxy;
+						return newclient.globalProxy;
+					}
 				}
 			}
 
-			if (prop === "$scramjet") return null;
+			if (prop === "$scramjet") return undefined;
 
 			if (typeof prop === "string" && UNSAFE_GLOBALS.includes(prop))
 				return client.wrapfn(value);