diff --git a/packages/bsky/src/api/app/bsky/unspecced/getTrendingTopics.ts b/packages/bsky/src/api/app/bsky/unspecced/getTrendingTopics.ts
index 2905702f219..a401c73fcd4 100644
--- a/packages/bsky/src/api/app/bsky/unspecced/getTrendingTopics.ts
+++ b/packages/bsky/src/api/app/bsky/unspecced/getTrendingTopics.ts
@@ -87,7 +87,7 @@ type Context = {
 }
 
 type Params = QueryParams & {
-  hydrateCtx: HydrateCtx & { viewer: string }
+  hydrateCtx: HydrateCtx & { viewer: string | null }
   headers: Record<string, string>
 }