diff --git a/src/routes/post/[slug]/+page.ts b/src/routes/post/[slug]/+page.ts
index a974f60..151f390 100644
--- a/src/routes/post/[slug]/+page.ts
+++ b/src/routes/post/[slug]/+page.ts
@@ -16,13 +16,13 @@ export const load: PageLoad = async ({ params }) => {
 			prevTitle?: string,
 			nextSlug?: string,
 			nextTitle?: string,
-		}[] = await Promise.all(post.metadata.series.map(async (series: string) => {
+		}[] = await Promise.all((metadata.series || []).map(async (series: string) => {
 			const postInSeries: Post[] = await getPosts({ series });
 
-			let prevSlug = null;
-			let prevTitle = null;
-			let nextSlug = null;
-			let nextTitle = null;
+			let prevSlug = undefined;
+			let prevTitle = undefined;
+			let nextSlug = undefined;
+			let nextTitle = undefined;
 
 			for (const p of postInSeries) {
 				if (p.date > metadata.date) {