diff --git a/pkg/contracts/preconf/preconf.go b/pkg/contracts/preconf/preconf.go
index d79f29c..c1360a1 100644
--- a/pkg/contracts/preconf/preconf.go
+++ b/pkg/contracts/preconf/preconf.go
@@ -121,9 +121,13 @@ func (p *preconfContract) OpenCommitment(
 	sharedSecretKey []byte,
 ) (common.Hash, error) {
 	bidAmt, _ := new(big.Int).SetString(bid, 10)
+	var eciBytes [32]byte
+	
+	copy(eciBytes[:], encryptedCommitmentIndex)
+
 	callData, err := p.preconfABI.Pack(
 		"openCommitment",
-		encryptedCommitmentIndex,
+		eciBytes,
 		bidAmt,
 		big.NewInt(blockNumber),
 		txnHash,