diff --git a/matrix-sdk-android/src/androidTest/java/im/vector/matrix/android/auth/AuthenticatorTest.kt b/matrix-sdk-android/src/androidTest/java/im/vector/matrix/android/auth/AuthenticatorTest.kt
index e0c1c0f5..fb0c6853 100644
--- a/matrix-sdk-android/src/androidTest/java/im/vector/matrix/android/auth/AuthenticatorTest.kt
+++ b/matrix-sdk-android/src/androidTest/java/im/vector/matrix/android/auth/AuthenticatorTest.kt
@@ -6,7 +6,6 @@ import android.support.test.runner.AndroidJUnit4
 import com.zhuinden.monarchy.Monarchy
 import im.vector.matrix.android.InstrumentedTest
 import im.vector.matrix.android.OkReplayRuleChainNoActivity
-import im.vector.matrix.android.api.MatrixOptions
 import im.vector.matrix.android.api.auth.Authenticator
 import im.vector.matrix.android.internal.auth.AuthModule
 import im.vector.matrix.android.internal.di.MatrixModule
@@ -26,7 +25,7 @@ internal class AuthenticatorTest : InstrumentedTest, KoinTest {
 
     init {
         Monarchy.init(context())
-        val matrixModule = MatrixModule(MatrixOptions(context())).definition
+        val matrixModule = MatrixModule(context()).definition
         val networkModule = NetworkModule().definition
         val authModule = AuthModule().definition
         loadKoinModules(listOf(matrixModule, networkModule, authModule))
diff --git a/matrix-sdk-android/src/androidTest/java/im/vector/matrix/android/session/room/timeline/ChunkEntityTest.kt b/matrix-sdk-android/src/androidTest/java/im/vector/matrix/android/session/room/timeline/ChunkEntityTest.kt
index 137ec790..181f0c1e 100644
--- a/matrix-sdk-android/src/androidTest/java/im/vector/matrix/android/session/room/timeline/ChunkEntityTest.kt
+++ b/matrix-sdk-android/src/androidTest/java/im/vector/matrix/android/session/room/timeline/ChunkEntityTest.kt
@@ -4,11 +4,7 @@ import com.zhuinden.monarchy.Monarchy
 import im.vector.matrix.android.InstrumentedTest
 import im.vector.matrix.android.api.session.events.model.Event
 import im.vector.matrix.android.api.session.events.model.EventType
-import im.vector.matrix.android.internal.database.helper.add
-import im.vector.matrix.android.internal.database.helper.addAll
-import im.vector.matrix.android.internal.database.helper.isUnlinked
-import im.vector.matrix.android.internal.database.helper.lastStateIndex
-import im.vector.matrix.android.internal.database.helper.merge
+import im.vector.matrix.android.internal.database.helper.*
 import im.vector.matrix.android.internal.database.model.ChunkEntity
 import im.vector.matrix.android.internal.session.room.timeline.PaginationDirection
 import io.realm.Realm
@@ -39,7 +35,7 @@ internal class ChunkEntityTest : InstrumentedTest {
         monarchy.runTransactionSync { realm ->
             val chunk: ChunkEntity = realm.createObject()
             val fakeEvent = createFakeEvent(false)
-            chunk.add(fakeEvent, PaginationDirection.FORWARDS)
+            chunk.add("roomId", fakeEvent, PaginationDirection.FORWARDS)
             chunk.events.size shouldEqual 1
         }
     }
@@ -49,8 +45,8 @@ internal class ChunkEntityTest : InstrumentedTest {
         monarchy.runTransactionSync { realm ->
             val chunk: ChunkEntity = realm.createObject()
             val fakeEvent = createFakeEvent(false)
-            chunk.add(fakeEvent, PaginationDirection.FORWARDS)
-            chunk.add(fakeEvent, PaginationDirection.FORWARDS)
+            chunk.add("roomId", fakeEvent, PaginationDirection.FORWARDS)
+            chunk.add("roomId", fakeEvent, PaginationDirection.FORWARDS)
             chunk.events.size shouldEqual 1
         }
     }
@@ -60,7 +56,7 @@ internal class ChunkEntityTest : InstrumentedTest {
         monarchy.runTransactionSync { realm ->
             val chunk: ChunkEntity = realm.createObject()
             val fakeEvent = createFakeEvent(true)
-            chunk.add(fakeEvent, PaginationDirection.FORWARDS)
+            chunk.add("roomId", fakeEvent, PaginationDirection.FORWARDS)
             chunk.lastStateIndex(PaginationDirection.FORWARDS) shouldEqual 1
         }
     }
@@ -70,7 +66,7 @@ internal class ChunkEntityTest : InstrumentedTest {
         monarchy.runTransactionSync { realm ->
             val chunk: ChunkEntity = realm.createObject()
             val fakeEvent = createFakeEvent(false)
-            chunk.add(fakeEvent, PaginationDirection.FORWARDS)
+            chunk.add("roomId", fakeEvent, PaginationDirection.FORWARDS)
             chunk.lastStateIndex(PaginationDirection.FORWARDS) shouldEqual 0
         }
     }
@@ -81,7 +77,7 @@ internal class ChunkEntityTest : InstrumentedTest {
             val chunk: ChunkEntity = realm.createObject()
             val fakeEvents = createFakeListOfEvents(30)
             val numberOfStateEvents = fakeEvents.filter { it.isStateEvent() }.size
-            chunk.addAll(fakeEvents, PaginationDirection.FORWARDS)
+            chunk.addAll("roomId", fakeEvents, PaginationDirection.FORWARDS)
             chunk.lastStateIndex(PaginationDirection.FORWARDS) shouldEqual numberOfStateEvents
         }
     }
@@ -94,7 +90,7 @@ internal class ChunkEntityTest : InstrumentedTest {
             val numberOfStateEvents = fakeEvents.filter { it.isStateEvent() }.size
             val lastIsState = fakeEvents.last().isStateEvent()
             val expectedStateIndex = if (lastIsState) -numberOfStateEvents + 1 else -numberOfStateEvents
-            chunk.addAll(fakeEvents, PaginationDirection.BACKWARDS)
+            chunk.addAll("roomId", fakeEvents, PaginationDirection.BACKWARDS)
             chunk.lastStateIndex(PaginationDirection.BACKWARDS) shouldEqual expectedStateIndex
         }
     }
@@ -104,20 +100,37 @@ internal class ChunkEntityTest : InstrumentedTest {
         monarchy.runTransactionSync { realm ->
             val chunk1: ChunkEntity = realm.createObject()
             val chunk2: ChunkEntity = realm.createObject()
-            chunk1.addAll(createFakeListOfEvents(30), PaginationDirection.BACKWARDS)
-            chunk2.addAll(createFakeListOfEvents(30), PaginationDirection.BACKWARDS)
+            chunk1.addAll("roomId", createFakeListOfEvents(30), PaginationDirection.BACKWARDS)
+            chunk2.addAll("roomId", createFakeListOfEvents(30), PaginationDirection.BACKWARDS)
             chunk1.merge(chunk2, PaginationDirection.BACKWARDS)
             chunk1.events.size shouldEqual 60
         }
     }
 
+    @Test
+    fun merge_shouldAddOnlyDifferentEvents_whenMergingBackward() {
+        monarchy.runTransactionSync { realm ->
+            val chunk1: ChunkEntity = realm.createObject()
+            val chunk2: ChunkEntity = realm.createObject()
+            val eventsForChunk1 = createFakeListOfEvents(30)
+            val eventsForChunk2 = eventsForChunk1 + createFakeListOfEvents(10)
+            chunk1.isLast = true
+            chunk2.isLast = false
+            chunk1.addAll("roomId", eventsForChunk1, PaginationDirection.FORWARDS)
+            chunk2.addAll("roomId", eventsForChunk2, PaginationDirection.BACKWARDS)
+            chunk1.merge(chunk2, PaginationDirection.BACKWARDS)
+            chunk1.events.size shouldEqual 40
+            chunk1.isLast.shouldBeTrue()
+        }
+    }
+
     @Test
     fun merge_shouldEventsBeLinked_whenMergingLinkedWithUnlinked() {
         monarchy.runTransactionSync { realm ->
             val chunk1: ChunkEntity = realm.createObject()
             val chunk2: ChunkEntity = realm.createObject()
-            chunk1.addAll(createFakeListOfEvents(30), PaginationDirection.BACKWARDS, isUnlinked = true)
-            chunk2.addAll(createFakeListOfEvents(30), PaginationDirection.BACKWARDS, isUnlinked = false)
+            chunk1.addAll("roomId", createFakeListOfEvents(30), PaginationDirection.BACKWARDS, isUnlinked = true)
+            chunk2.addAll("roomId", createFakeListOfEvents(30), PaginationDirection.BACKWARDS, isUnlinked = false)
             chunk1.merge(chunk2, PaginationDirection.BACKWARDS)
             chunk1.isUnlinked().shouldBeFalse()
         }
@@ -128,8 +141,8 @@ internal class ChunkEntityTest : InstrumentedTest {
         monarchy.runTransactionSync { realm ->
             val chunk1: ChunkEntity = realm.createObject()
             val chunk2: ChunkEntity = realm.createObject()
-            chunk1.addAll(createFakeListOfEvents(30), PaginationDirection.BACKWARDS, isUnlinked = true)
-            chunk2.addAll(createFakeListOfEvents(30), PaginationDirection.BACKWARDS, isUnlinked = true)
+            chunk1.addAll("roomId", createFakeListOfEvents(30), PaginationDirection.BACKWARDS, isUnlinked = true)
+            chunk2.addAll("roomId", createFakeListOfEvents(30), PaginationDirection.BACKWARDS, isUnlinked = true)
             chunk1.merge(chunk2, PaginationDirection.BACKWARDS)
             chunk1.isUnlinked().shouldBeTrue()
         }
@@ -142,8 +155,8 @@ internal class ChunkEntityTest : InstrumentedTest {
             val chunk2: ChunkEntity = realm.createObject()
             val prevToken = "prev_token"
             chunk1.prevToken = prevToken
-            chunk1.addAll(createFakeListOfEvents(30), PaginationDirection.BACKWARDS, isUnlinked = true)
-            chunk2.addAll(createFakeListOfEvents(30), PaginationDirection.BACKWARDS, isUnlinked = true)
+            chunk1.addAll("roomId", createFakeListOfEvents(30), PaginationDirection.BACKWARDS, isUnlinked = true)
+            chunk2.addAll("roomId", createFakeListOfEvents(30), PaginationDirection.BACKWARDS, isUnlinked = true)
             chunk1.merge(chunk2, PaginationDirection.FORWARDS)
             chunk1.prevToken shouldEqual prevToken
         }
@@ -156,8 +169,8 @@ internal class ChunkEntityTest : InstrumentedTest {
             val chunk2: ChunkEntity = realm.createObject()
             val nextToken = "next_token"
             chunk1.nextToken = nextToken
-            chunk1.addAll(createFakeListOfEvents(30), PaginationDirection.BACKWARDS, isUnlinked = true)
-            chunk2.addAll(createFakeListOfEvents(30), PaginationDirection.BACKWARDS, isUnlinked = true)
+            chunk1.addAll("roomId", createFakeListOfEvents(30), PaginationDirection.BACKWARDS, isUnlinked = true)
+            chunk2.addAll("roomId", createFakeListOfEvents(30), PaginationDirection.BACKWARDS, isUnlinked = true)
             chunk1.merge(chunk2, PaginationDirection.BACKWARDS)
             chunk1.nextToken shouldEqual nextToken
         }
diff --git a/matrix-sdk-android/src/androidTest/java/im/vector/matrix/android/session/room/timeline/RoomDataHelper.kt b/matrix-sdk-android/src/androidTest/java/im/vector/matrix/android/session/room/timeline/RoomDataHelper.kt
index 2385d794..c7279bf2 100644
--- a/matrix-sdk-android/src/androidTest/java/im/vector/matrix/android/session/room/timeline/RoomDataHelper.kt
+++ b/matrix-sdk-android/src/androidTest/java/im/vector/matrix/android/session/room/timeline/RoomDataHelper.kt
@@ -34,7 +34,7 @@ object RoomDataHelper {
                 prevToken = Random.nextLong(System.currentTimeMillis()).toString()
                 isLast = true
             }
-            chunkEntity.addAll(eventList, PaginationDirection.FORWARDS)
+            chunkEntity.addAll("roomId", eventList, PaginationDirection.FORWARDS)
             roomEntity.addOrUpdate(chunkEntity)
         }
     }
diff --git a/matrix-sdk-android/src/androidTest/java/im/vector/matrix/android/session/room/timeline/TimelineHolderTest.kt b/matrix-sdk-android/src/androidTest/java/im/vector/matrix/android/session/room/timeline/TimelineHolderTest.kt
index fc8731ab..38b465d8 100644
--- a/matrix-sdk-android/src/androidTest/java/im/vector/matrix/android/session/room/timeline/TimelineHolderTest.kt
+++ b/matrix-sdk-android/src/androidTest/java/im/vector/matrix/android/session/room/timeline/TimelineHolderTest.kt
@@ -6,10 +6,11 @@ import com.zhuinden.monarchy.Monarchy
 import im.vector.matrix.android.InstrumentedTest
 import im.vector.matrix.android.LiveDataTestObserver
 import im.vector.matrix.android.api.thread.MainThreadExecutor
-import im.vector.matrix.android.internal.task.TaskExecutor
+import im.vector.matrix.android.internal.session.room.members.RoomMemberExtractor
 import im.vector.matrix.android.internal.session.room.timeline.DefaultTimelineHolder
 import im.vector.matrix.android.internal.session.room.timeline.TimelineBoundaryCallback
 import im.vector.matrix.android.internal.session.room.timeline.TokenChunkEventPersistor
+import im.vector.matrix.android.internal.task.TaskExecutor
 import im.vector.matrix.android.internal.util.PagingRequestHelper
 import im.vector.matrix.android.testCoroutineDispatchers
 import io.realm.Realm
@@ -43,7 +44,7 @@ internal class TimelineHolderTest : InstrumentedTest {
         val boundaryCallback = TimelineBoundaryCallback(roomId, taskExecutor, paginationTask, monarchy, PagingRequestHelper(MainThreadExecutor()))
 
         RoomDataHelper.fakeInitialSync(monarchy, roomId)
-        val timelineHolder = DefaultTimelineHolder(roomId, monarchy, taskExecutor, boundaryCallback, getContextOfEventTask)
+        val timelineHolder = DefaultTimelineHolder(roomId, monarchy, taskExecutor, boundaryCallback, getContextOfEventTask, RoomMemberExtractor(monarchy, roomId))
         val timelineObserver = LiveDataTestObserver.test(timelineHolder.timeline())
         timelineObserver.awaitNextValue().assertHasValue()
         var pagedList = timelineObserver.value()
diff --git a/matrix-sdk-android/src/main/java/im/vector/matrix/android/api/Matrix.kt b/matrix-sdk-android/src/main/java/im/vector/matrix/android/api/Matrix.kt
index 714ac0f7..467329c8 100644
--- a/matrix-sdk-android/src/main/java/im/vector/matrix/android/api/Matrix.kt
+++ b/matrix-sdk-android/src/main/java/im/vector/matrix/android/api/Matrix.kt
@@ -12,6 +12,7 @@ import im.vector.matrix.android.internal.di.MatrixModule
 import im.vector.matrix.android.internal.di.NetworkModule
 import im.vector.matrix.android.internal.util.BackgroundDetectionObserver
 import org.koin.standalone.inject
+import java.util.concurrent.atomic.AtomicBoolean
 
 
 class Matrix private constructor(context: Context) : MatrixKoinComponent {
@@ -40,9 +41,12 @@ class Matrix private constructor(context: Context) : MatrixKoinComponent {
 
     companion object {
         private lateinit var instance: Matrix
+        private val isInit = AtomicBoolean(false)
 
         internal fun initialize(context: Context) {
-            instance = Matrix(context.applicationContext)
+            if (isInit.compareAndSet(false, true)) {
+                instance = Matrix(context.applicationContext)
+            }
         }
 
         fun getInstance(): Matrix {