diff --git a/ios/IndySdk.swift b/ios/IndySdk.swift
index f0d2ab5..d680ace 100644
--- a/ios/IndySdk.swift
+++ b/ios/IndySdk.swift
@@ -208,7 +208,7 @@ class IndySdk : NSObject {
         IndyCrypto.verifySignature(signatureData, forMessage: messageData, key: signerVk, completion: completionWithBool(resolve, reject))
     }
     
-    @objc func packMessage(_ wh: NSNumber, message: Array<UInt8>, receiverKeys: String, senderVk: String, resolver resolve: @escaping RCTPromiseResolveBlock, rejecter reject: @escaping RCTPromiseRejectBlock) -> Void {
+    @objc func packMessage(_ wh: NSNumber, message: Array<UInt8>, receiverKeys: String, senderVk: String?, resolver resolve: @escaping RCTPromiseResolveBlock, rejecter reject: @escaping RCTPromiseRejectBlock) -> Void {
         let whNumber = Int32(truncating: wh)
         let messageData = Data(message)
         IndyCrypto.packMessage(messageData, receivers: receiverKeys, sender: senderVk, walletHandle: whNumber, completion: completionWithData(resolve, reject))
diff --git a/src/index.js b/src/index.js
index 53574c3..a80ac77 100644
--- a/src/index.js
+++ b/src/index.js
@@ -413,7 +413,12 @@ const indy = {
     return IndySdk.cryptoVerify(signerVk, Array.from(message), Array.from(signature))
   },
 
-  async packMessage(wh: WalletHandle, message: Buffer, receiverKeys: Verkey[], senderVk: string): Promise<Buffer> {
+  async packMessage(
+    wh: WalletHandle,
+    message: Buffer,
+    receiverKeys: Verkey[],
+    senderVk: string | null
+  ): Promise<Buffer> {
     if (Platform.OS == 'ios') {
       return Buffer.from(await IndySdk.packMessage(wh, Array.from(message), JSON.stringify(receiverKeys), senderVk))
     }