diff --git a/backend/mpc-system/services/service-party-app/tss-party/main.go b/backend/mpc-system/services/service-party-app/tss-party/main.go
index 75dd00cb..43023996 100644
--- a/backend/mpc-system/services/service-party-app/tss-party/main.go
+++ b/backend/mpc-system/services/service-party-app/tss-party/main.go
@@ -597,9 +597,13 @@ func executeSign(
 	// Create peer context and parameters
 	// For signing with T parties from an N-party keygen:
 	// - The peer context contains only the T signing parties
-	// - threshold parameter should be T-1 (since we need T parties to sign, threshold = T-1)
+	// - IMPORTANT: partyCount must be the original N from keygen, NOT current signers count
+	// - threshold must be the original T from keygen, NOT T-1
+	// This matches how pkg/tss/signing.go creates parameters in server-party:
+	//   params := tss.NewParameters(tss.S256(), peerCtx, selfTSSID, config.TotalParties, config.Threshold)
+	// where TotalParties=N from keygen and Threshold=T from keygen
 	peerCtx := tss.NewPeerContext(sortedPartyIDs)
-	params := tss.NewParameters(tss.S256(), peerCtx, selfTSSID, len(sortedPartyIDs), thresholdT-1)
+	params := tss.NewParameters(tss.S256(), peerCtx, selfTSSID, thresholdN, thresholdT)
 
 	// Create channels
 	outCh := make(chan tss.Message, thresholdT*10)