diff --git a/src/fetch.ts b/src/fetch.ts
index 162ea45..5a6cd0e 100644
--- a/src/fetch.ts
+++ b/src/fetch.ts
@@ -49,7 +49,7 @@ export interface FetchEventSourceInit extends RequestInit {
      */
     openWhenHidden?: boolean;
 
-    /** The Fetch function to use. Defaults to window.fetch */
+    /** The Fetch function to use. Defaults to globalThis.fetch */
     fetch?: typeof fetch;
 }
 
@@ -84,10 +84,10 @@ export function fetchEventSource(input: RequestInfo, {
         }
 
         let retryInterval = DefaultRetryInterval;
-        let retryTimer = 0;
+        let retryTimer: number = 0;
         function dispose() {
             document.removeEventListener('visibilitychange', onVisibilityChange);
-            window.clearTimeout(retryTimer);
+            globalThis.clearTimeout(retryTimer);
             curRequestController.abort();
         }
 
@@ -97,7 +97,7 @@ export function fetchEventSource(input: RequestInfo, {
             resolve(); // don't waste time constructing/logging errors
         });
 
-        const fetch = inputFetch ?? window.fetch;
+        const fetch = inputFetch ?? globalThis.fetch;
         const onopen = inputOnOpen ?? defaultOnOpen;
         async function create() {
             curRequestController = new AbortController();
@@ -131,8 +131,8 @@ export function fetchEventSource(input: RequestInfo, {
                     try {
                         // check if we need to retry:
                         const interval: any = onerror?.(err) ?? retryInterval;
-                        window.clearTimeout(retryTimer);
-                        retryTimer = window.setTimeout(create, interval);
+                        globalThis.clearTimeout(retryTimer);
+                        retryTimer = globalThis.setTimeout(create, interval) as unknown as number;
                     } catch (innerErr) {
                         // we should not retry anymore:
                         dispose();