diff --git a/src/secret-box.ts b/src/secret-box.ts
index 065482a..4922c61 100644
--- a/src/secret-box.ts
+++ b/src/secret-box.ts
@@ -24,7 +24,7 @@ export default class SecretBox {
 
   public static async encrypt(data: Uint8Array, key: CryptoKey): Promise<SecretBox> {
     log.trace('encrypt')
-    const iv = crypto.getRandomValues(new Uint8Array(11))
+    const iv = crypto.getRandomValues(new Uint8Array(12))
     const cipher = await crypto.subtle.encrypt(
       {
         name: consts.ENCRYPTION,