diff --git a/src/index.d.ts b/src/index.d.ts
index 26e3caf..74de0fc 100644
--- a/src/index.d.ts
+++ b/src/index.d.ts
@@ -31,7 +31,7 @@ declare namespace PeerId {
     /**
      * Private key.
      */
-    privKey: string;
+    privKey?: string;
   };
 
   /**