diff --git a/sandpack-react/src/presets/CustomSandpack.stories.tsx b/sandpack-react/src/presets/CustomSandpack.stories.tsx
index ce5276ff..6044a2b1 100644
--- a/sandpack-react/src/presets/CustomSandpack.stories.tsx
+++ b/sandpack-react/src/presets/CustomSandpack.stories.tsx
@@ -55,8 +55,8 @@ export const ExperimentalServiceWorker: React.FC = () => {
         `,
       }}
       options={{
-        bundlerURL: "https://nqfrns-3000.csb.app/",
         experimental_enableServiceWorker: true,
+        experimental_enableStableServiceWorkerId: true,
       }}
       template="react"
     />
diff --git a/sandpack-react/src/utils/useAsyncSandpackId.ts b/sandpack-react/src/utils/useAsyncSandpackId.ts
index b4b0dd81..312bb281 100644
--- a/sandpack-react/src/utils/useAsyncSandpackId.ts
+++ b/sandpack-react/src/utils/useAsyncSandpackId.ts
@@ -29,7 +29,10 @@ export const useAsyncSandpackId = (files: SandpackBundlerFiles) => {
         .join("|||");
       const sha = await generateShortId(allCode + reactDomId);
 
-      return ensureLength(sha.replace(/:/g, "sp"), MAX_ID_LENGTH);
+      return ensureLength(
+        sha.replace(/:/g, "sp").replace(/[^a-zA-Z]/g, ""),
+        MAX_ID_LENGTH
+      );
     };
   } else {
     return () => ensureLength(generateRandomId(), MAX_ID_LENGTH);