diff --git a/.changeset/long-timers-try.md b/.changeset/long-timers-try.md
new file mode 100644
index 000000000000..aa86bafaa24e
--- /dev/null
+++ b/.changeset/long-timers-try.md
@@ -0,0 +1,5 @@
+---
+'@sveltejs/adapter-vercel': patch
+---
+
+fix: mark `expiration` as required
diff --git a/packages/adapter-vercel/index.d.ts b/packages/adapter-vercel/index.d.ts
index a4e21982dfa8..cdfa2d324a49 100644
--- a/packages/adapter-vercel/index.d.ts
+++ b/packages/adapter-vercel/index.d.ts
@@ -35,7 +35,7 @@ export interface ServerlessConfig {
 		/**
 		 * Expiration time (in seconds) before the cached asset will be re-generated by invoking the Serverless Function. Setting the value to `false` means it will never expire.
 		 */
-		expiration?: number | false;
+		expiration: number | false;
 		/**
 		 * Option group number of the asset. Assets with the same group number will all be re-validated at the same time.
 		 */