diff --git a/src/content/config.ts b/src/content/config.ts
index 82637f0e..8f5153f2 100644
--- a/src/content/config.ts
+++ b/src/content/config.ts
@@ -29,7 +29,7 @@ const talkCollection = defineCollection({
         location: z.string().optional(),
         name: z.string(),
         online: z.boolean().optional(),
-        url: z.string().optional(),
+        url: z.string().or(z.null()).optional(),
       })
     ),
     speakerdeck: z