diff --git a/Polkadot/Polkadot-starter/src/mappings/mappingHandlers.ts b/Polkadot/Polkadot-starter/src/mappings/mappingHandlers.ts
index 3cd4d9ce..1820ae90 100644
--- a/Polkadot/Polkadot-starter/src/mappings/mappingHandlers.ts
+++ b/Polkadot/Polkadot-starter/src/mappings/mappingHandlers.ts
@@ -1,3 +1,4 @@
+import assert from 'assert';
 import {
   SubstrateExtrinsic,
   SubstrateEvent,
@@ -25,10 +26,13 @@ export async function handleEvent(event: SubstrateEvent): Promise<void> {
   // logger.info(JSON.stringify(event));
   const {
     event: {
-      data: [from, to, amount],
+      data: [to, amount],
     },
   } = event;
 
+  const from = event.extrinsic?.extrinsic.signer;
+  assert(from, "Signer is missing");
+
   const blockNumber: number = event.block.block.header.number.toNumber();
 
   const fromAccount = await checkAndGetAccount(from.toString(), blockNumber);