diff --git a/index.d.ts b/index.d.ts
index 3489c27..e927a4b 100644
--- a/index.d.ts
+++ b/index.d.ts
@@ -715,6 +715,14 @@ declare global {
                 : string
     }
 
+    interface Base64Package {
+        encode(data: string|Int8Array): string
+        decode(data: string): string
+        decode(data: string, options: {returnBytes: true}): Int8Array
+        decode(data: string, options: {returnBytes: false}): string
+        decode(data: string, options: {returnBytes?: boolean}): string | Int8Array
+    }
+
     export interface HookContext
         extends GetHookData,
             GetHookGetOnlyData,