diff --git a/matrix-sdk-android/src/main/java/org/matrix/android/sdk/internal/session/sync/SyncResponsePostTreatmentAggregatorHandler.kt b/matrix-sdk-android/src/main/java/org/matrix/android/sdk/internal/session/sync/SyncResponsePostTreatmentAggregatorHandler.kt
index e074cddc1f..db1100d76c 100644
--- a/matrix-sdk-android/src/main/java/org/matrix/android/sdk/internal/session/sync/SyncResponsePostTreatmentAggregatorHandler.kt
+++ b/matrix-sdk-android/src/main/java/org/matrix/android/sdk/internal/session/sync/SyncResponsePostTreatmentAggregatorHandler.kt
@@ -17,6 +17,7 @@
 package org.matrix.android.sdk.internal.session.sync
 
 import org.matrix.android.sdk.api.MatrixPatterns
+import org.matrix.android.sdk.internal.session.sync.model.accountdata.toMutable
 import org.matrix.android.sdk.internal.session.user.accountdata.DirectChatsHelper
 import org.matrix.android.sdk.internal.session.user.accountdata.UpdateUserAccountDataTask
 import javax.inject.Inject
@@ -38,7 +39,7 @@ internal class SyncResponsePostTreatmentAggregatorHandler @Inject constructor(
     }
 
     private suspend fun updateDirectUserIds(directUserIdsToUpdate: Map<String, String>) {
-        val directChats = directChatsHelper.getLocalDirectMessages()
+        val directChats = directChatsHelper.getLocalDirectMessages().toMutable()
         var hasUpdate = false
         directUserIdsToUpdate.forEach { (roomId, candidateUserId) ->
             // consider room is a DM if referenced in the DM dictionary
diff --git a/matrix-sdk-android/src/main/java/org/matrix/android/sdk/internal/session/sync/UserAccountDataSyncHandler.kt b/matrix-sdk-android/src/main/java/org/matrix/android/sdk/internal/session/sync/UserAccountDataSyncHandler.kt
index c23421281c..110e77813d 100644
--- a/matrix-sdk-android/src/main/java/org/matrix/android/sdk/internal/session/sync/UserAccountDataSyncHandler.kt
+++ b/matrix-sdk-android/src/main/java/org/matrix/android/sdk/internal/session/sync/UserAccountDataSyncHandler.kt
@@ -53,6 +53,7 @@ import org.matrix.android.sdk.internal.session.sync.model.accountdata.Breadcrumb
 import org.matrix.android.sdk.internal.session.sync.model.accountdata.DirectMessagesContent
 import org.matrix.android.sdk.internal.session.sync.model.accountdata.IgnoredUsersContent
 import org.matrix.android.sdk.internal.session.sync.model.accountdata.UserAccountDataSync
+import org.matrix.android.sdk.internal.session.sync.model.accountdata.toMutable
 import org.matrix.android.sdk.internal.session.user.accountdata.DirectChatsHelper
 import org.matrix.android.sdk.internal.session.user.accountdata.UpdateUserAccountDataTask
 import timber.log.Timber
@@ -83,7 +84,7 @@ internal class UserAccountDataSyncHandler @Inject constructor(
     // If we get some direct chat invites, we synchronize the user account data including those.
     suspend fun synchronizeWithServerIfNeeded(invites: Map<String, InvitedRoomSync>) {
         if (invites.isNullOrEmpty()) return
-        val directChats = directChatsHelper.getLocalDirectMessages()
+        val directChats = directChatsHelper.getLocalDirectMessages().toMutable()
         var hasUpdate = false
         monarchy.doWithRealm { realm ->
             invites.forEach { (roomId, _) ->
diff --git a/matrix-sdk-android/src/main/java/org/matrix/android/sdk/internal/session/sync/model/accountdata/DirectMessagesContent.kt b/matrix-sdk-android/src/main/java/org/matrix/android/sdk/internal/session/sync/model/accountdata/DirectMessagesContent.kt
index 06ae7b9a8f..7c73f1fed0 100644
--- a/matrix-sdk-android/src/main/java/org/matrix/android/sdk/internal/session/sync/model/accountdata/DirectMessagesContent.kt
+++ b/matrix-sdk-android/src/main/java/org/matrix/android/sdk/internal/session/sync/model/accountdata/DirectMessagesContent.kt
@@ -19,4 +19,13 @@ package org.matrix.android.sdk.internal.session.sync.model.accountdata
 /**
  * Keys are userIds, values are list of roomIds
  */
-internal typealias DirectMessagesContent = MutableMap<String, MutableList<String>>
+internal typealias DirectMessagesContent = Map<String, List<String>>
+
+/**
+ * Returns a new [MutableMap] with all elements of this collection.
+ */
+internal fun DirectMessagesContent.toMutable(): MutableMap<String, MutableList<String>> {
+    return map { it.key to it.value.toMutableList() }
+            .toMap()
+            .toMutableMap()
+}