diff --git a/web/apps/cast/src/pages/slideshow.tsx b/web/apps/cast/src/pages/slideshow.tsx
index c3e950783..6d1eee605 100644
--- a/web/apps/cast/src/pages/slideshow.tsx
+++ b/web/apps/cast/src/pages/slideshow.tsx
@@ -36,9 +36,10 @@ export default function Slideshow() {
     };
 
     const advance = async () => {
+        console.log("in advance");
         if (!urlGenerator) throw new Error("Unexpected state");
-        const urls = await urlGenerator.next();
-        if (!urls) {
+        const { value: urls, done } = await urlGenerator.next();
+        if (done) {
             log.warn("Empty collection");
             // Go back to pairing page
             router.push("/");
@@ -182,7 +183,10 @@ export default function Slideshow() {
         };
     }, [loading]);
 
-    if (loading) return <PairedSuccessfullyOverlay />;
+    console.log({ a: "render", loading, currentFileURL, nextFileURL });
+
+    if (loading || !currentFileURL || !nextFileURL)
+        return <PairedSuccessfullyOverlay />;
 
     return <SlideView url={currentFileURL} nextURL={nextFileURL} />;
 }
diff --git a/web/apps/cast/src/services/cast.ts b/web/apps/cast/src/services/cast.ts
index 4312178c3..af069dfcf 100644
--- a/web/apps/cast/src/services/cast.ts
+++ b/web/apps/cast/src/services/cast.ts
@@ -78,15 +78,15 @@ export const readCastData = (): CastData => {
  * collection, and just moves onward to the next one. It will however throw if
  * there are errors in getting the collection itself.
  *
- * If there are no renderable image in the collection, it resolves with
- * `undefined`.
+ * If there are no renderable image in the collection, the sequence ends by
+ * yielding `done: true`.
  *
  * @param castData The collection to show and credentials to fetch the files
  * within it.
  */
 export const renderableURLs = async function* (castData: CastData) {
     const { collectionKey, castToken } = castData;
-    let previousURL: string | undefined
+    let previousURL: string | undefined;
     while (true) {
         const collection = await getCollection(castToken, collectionKey);
         await syncPublicFiles(castToken, collection, () => {});
@@ -94,6 +94,7 @@ export const renderableURLs = async function* (castData: CastData) {
         const files = allFiles.filter((file) => isFileEligibleForCast(file));
 
         for (const file of files) {
+            console.log("in generator", previousURL);
             if (!previousURL) {
                 previousURL = await createRenderableURL(castToken, file);
                 continue;