diff --git a/src/index.ts b/src/index.ts
index 03e7d5e..6147d7f 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -144,6 +144,11 @@ export const app = new Elysia()
     const id = Math.random().toString().substring(2, 10)
     let metadata = await getMetadata()
 
+    // Check duplicate owner key
+    if (metadata.find((p) => p.owner_key === owner_key)) {
+      done(400, "Owner key already in use. Please use a unique owner key.")
+    }
+
     // Process and save files
     // We use {id}-1 and {id}-2 as requested by "{id}-{number}"
     const originalExt = photo.name.split(".").pop() || "jpg"