diff --git a/matrix-sdk-android/src/main/java/org/matrix/android/sdk/internal/session/room/aggregation/utd/EncryptedReferenceAggregationProcessor.kt b/matrix-sdk-android/src/main/java/org/matrix/android/sdk/internal/session/room/aggregation/utd/EncryptedReferenceAggregationProcessor.kt
index fdd3bc80e3..8987e837bc 100644
--- a/matrix-sdk-android/src/main/java/org/matrix/android/sdk/internal/session/room/aggregation/utd/EncryptedReferenceAggregationProcessor.kt
+++ b/matrix-sdk-android/src/main/java/org/matrix/android/sdk/internal/session/room/aggregation/utd/EncryptedReferenceAggregationProcessor.kt
@@ -43,7 +43,9 @@ class EncryptedReferenceAggregationProcessor @Inject constructor() {
     ) {
         event.eventId?.let { eventId ->
             val existingRelatedPoll = getPollSummaryWithEventId(realm, relatedEventId)
-            existingRelatedPoll?.encryptedRelatedEventIds?.add(eventId)
+            if (eventId !in existingRelatedPoll?.encryptedRelatedEventIds.orEmpty()) {
+                existingRelatedPoll?.encryptedRelatedEventIds?.add(eventId)
+            }
         }
     }