diff --git a/src/interface.ts b/src/interface.ts
index 62c9a53..7035717 100644
--- a/src/interface.ts
+++ b/src/interface.ts
@@ -2,7 +2,7 @@ export interface IBls {
   PrivateKey: {
     fromBytes(bytes: Uint8Array): IPrivateKey;
     fromHex(hex: string): IPrivateKey;
-    fromKeygen(): IPrivateKey;
+    fromKeygen(ikm?: Uint8Array): IPrivateKey;
   };
   PublicKey: {
     fromBytes(bytes: Uint8Array): IPublicKey;