diff --git a/backend/mpc-system/services/service-party-android/app/src/main/java/com/durian/tssparty/data/repository/TssRepository.kt b/backend/mpc-system/services/service-party-android/app/src/main/java/com/durian/tssparty/data/repository/TssRepository.kt
index 98e62d39..062880d7 100644
--- a/backend/mpc-system/services/service-party-android/app/src/main/java/com/durian/tssparty/data/repository/TssRepository.kt
+++ b/backend/mpc-system/services/service-party-android/app/src/main/java/com/durian/tssparty/data/repository/TssRepository.kt
@@ -2089,8 +2089,39 @@ class TssRepository @Inject constructor(
                 android.util.Log.d("TssRepository", "[EXPORT]   - publicKey length: ${share.publicKey.length}")
                 android.util.Log.d("TssRepository", "[EXPORT]   - encryptedShare length: ${share.encryptedShare.length}")
 
-                android.util.Log.d("TssRepository", "[EXPORT] Converting to ShareBackup...")
-                val backup = ShareBackup.fromShareRecord(share.toShareRecord())
+                // If partyId is empty (legacy data from before MIGRATION_2_3), fetch it from backend
+                var effectivePartyId = share.partyId
+                if (effectivePartyId.isEmpty()) {
+                    android.util.Log.w("TssRepository", "[EXPORT] partyId is empty (legacy data), fetching from backend...")
+                    try {
+                        val sessionStatusResult = getSessionStatus(share.sessionId)
+                        if (sessionStatusResult.isSuccess) {
+                            val sessionStatus = sessionStatusResult.getOrThrow()
+                            // Find participant by partyIndex
+                            val participant = sessionStatus.participants.find { it.partyIndex == share.partyIndex }
+                            if (participant != null && participant.partyId.isNotEmpty()) {
+                                effectivePartyId = participant.partyId
+                                android.util.Log.d("TssRepository", "[EXPORT] Retrieved partyId from backend: $effectivePartyId")
+
+                                // Also update the database for future exports
+                                val updatedShare = share.copy(partyId = effectivePartyId)
+                                shareRecordDao.insertShare(updatedShare)
+                                android.util.Log.d("TssRepository", "[EXPORT] Updated partyId in database")
+                            } else {
+                                android.util.Log.w("TssRepository", "[EXPORT] Could not find participant with partyIndex=${share.partyIndex} in session")
+                            }
+                        } else {
+                            android.util.Log.w("TssRepository", "[EXPORT] Failed to get session status: ${sessionStatusResult.exceptionOrNull()?.message}")
+                        }
+                    } catch (e: Exception) {
+                        android.util.Log.w("TssRepository", "[EXPORT] Error fetching partyId from backend: ${e.message}")
+                    }
+                }
+
+                android.util.Log.d("TssRepository", "[EXPORT] Converting to ShareBackup with partyId: $effectivePartyId")
+                // Create ShareRecord with effective partyId (may be fetched from backend)
+                val shareRecord = share.toShareRecord().copy(partyId = effectivePartyId)
+                val backup = ShareBackup.fromShareRecord(shareRecord)
                 android.util.Log.d("TssRepository", "[EXPORT] ShareBackup created, version: ${backup.version}")
 
                 android.util.Log.d("TssRepository", "[EXPORT] Serializing to JSON...")