diff --git a/matrix-sdk-android/src/main/java/im/vector/matrix/android/api/session/room/model/message/MessageContent.kt b/matrix-sdk-android/src/main/java/im/vector/matrix/android/api/session/room/model/message/MessageContent.kt
index c45e47fc..bd32a75a 100644
--- a/matrix-sdk-android/src/main/java/im/vector/matrix/android/api/session/room/model/message/MessageContent.kt
+++ b/matrix-sdk-android/src/main/java/im/vector/matrix/android/api/session/room/model/message/MessageContent.kt
@@ -25,4 +25,9 @@ interface MessageContent {
     val body: String
     val relatesTo: RelationDefaultContent?
     val newContent: Content?
+}
+
+
+fun MessageContent?.isReply(): Boolean {
+    return this?.relatesTo?.inReplyTo != null
 }
\ No newline at end of file
diff --git a/matrix-sdk-android/src/main/java/im/vector/matrix/android/api/session/room/model/relation/RelationService.kt b/matrix-sdk-android/src/main/java/im/vector/matrix/android/api/session/room/model/relation/RelationService.kt
index bfc569e1..da91ee70 100644
--- a/matrix-sdk-android/src/main/java/im/vector/matrix/android/api/session/room/model/relation/RelationService.kt
+++ b/matrix-sdk-android/src/main/java/im/vector/matrix/android/api/session/room/model/relation/RelationService.kt
@@ -84,7 +84,9 @@ interface RelationService {
     /**
      * Edit a reply. This is a special case because replies contains fallback text as a prefix.
      * This method will take the new body (stripped from fallbacks) and re-add them before sending.
-     * @param targetEventId The event to edit
+     * @param replyToEdit The event to edit
+     * @param originalSenderId the sender of the message that this reply (being edited) is relating to
+     * @param originalEventId the event id that this reply (being edited) is relating to
      * @param newBodyText The edited body (stripped from in reply to content)
      * @param compatibilityBodyText The text that will appear on clients that don't support yet edition
      */
diff --git a/matrix-sdk-android/src/main/java/im/vector/matrix/android/api/session/room/timeline/TimelineEvent.kt b/matrix-sdk-android/src/main/java/im/vector/matrix/android/api/session/room/timeline/TimelineEvent.kt
index 251fe3d3..761c3961 100644
--- a/matrix-sdk-android/src/main/java/im/vector/matrix/android/api/session/room/timeline/TimelineEvent.kt
+++ b/matrix-sdk-android/src/main/java/im/vector/matrix/android/api/session/room/timeline/TimelineEvent.kt
@@ -21,8 +21,9 @@ import im.vector.matrix.android.api.session.events.model.EventType
 import im.vector.matrix.android.api.session.events.model.toModel
 import im.vector.matrix.android.api.session.room.model.EventAnnotationsSummary
 import im.vector.matrix.android.api.session.room.model.message.MessageContent
+import im.vector.matrix.android.api.session.room.model.message.isReply
 import im.vector.matrix.android.api.session.room.send.SendState
-import im.vector.matrix.android.internal.session.room.send.extractUsefulTextFromReply
+import im.vector.matrix.android.api.util.ContentUtils.extractUsefulTextFromReply
 
 /**
  * This data class is a wrapper around an Event. It allows to get useful data in the context of a timeline.
@@ -93,7 +94,7 @@ fun TimelineEvent.getLastMessageContent(): MessageContent? = annotations?.editSu
 
 fun TimelineEvent.getTextEditableContent(): String? {
     val originalContent = root.getClearContent().toModel<MessageContent>() ?: return null
-    val isReply = originalContent.relatesTo?.inReplyTo != null
+    val isReply = originalContent.isReply()
     val lastContent = getLastMessageContent()
     return if (isReply) {
         return extractUsefulTextFromReply(lastContent?.body ?: "")
diff --git a/matrix-sdk-android/src/main/java/im/vector/matrix/android/api/util/ContentUtils.kt b/matrix-sdk-android/src/main/java/im/vector/matrix/android/api/util/ContentUtils.kt
index 0a395dee..ad17d26b 100644
--- a/matrix-sdk-android/src/main/java/im/vector/matrix/android/api/util/ContentUtils.kt
+++ b/matrix-sdk-android/src/main/java/im/vector/matrix/android/api/util/ContentUtils.kt
@@ -38,7 +38,9 @@ object ContentUtils {
 
     fun extractUsefulTextFromHtmlReply(repliedBody: String): String {
         if (repliedBody.startsWith("<mx-reply>")) {
-            return repliedBody.substring(repliedBody.lastIndexOf("</mx-reply>") + "</mx-reply>".length).trim()
+            val closingTagIndex = repliedBody.lastIndexOf("</mx-reply>")
+            if (closingTagIndex != -1)
+                return repliedBody.substring(closingTagIndex + "</mx-reply>".length).trim()
         }
         return repliedBody
     }
diff --git a/matrix-sdk-android/src/main/java/im/vector/matrix/android/internal/session/room/send/LocalEchoEventFactory.kt b/matrix-sdk-android/src/main/java/im/vector/matrix/android/internal/session/room/send/LocalEchoEventFactory.kt
index fe039341..51aed8a7 100644
--- a/matrix-sdk-android/src/main/java/im/vector/matrix/android/internal/session/room/send/LocalEchoEventFactory.kt
+++ b/matrix-sdk-android/src/main/java/im/vector/matrix/android/internal/session/room/send/LocalEchoEventFactory.kt
@@ -334,8 +334,8 @@ internal class LocalEchoEventFactory @Inject constructor(private val credentials
                         formattedText = content.formattedBody
                     }
                 }
-                val isReply = content.relatesTo?.inReplyTo?.eventId != null ||
-                        originalContent?.relatesTo?.inReplyTo?.eventId != null
+                val isReply = content.isReply() ||
+                        originalContent.isReply()
                 return if (isReply)
                     TextContent(content.body, formattedText).removeInReplyFallbacks()
                 else
diff --git a/vector/src/main/java/im/vector/riotx/features/home/room/detail/timeline/action/ViewEditHistoryViewModel.kt b/vector/src/main/java/im/vector/riotx/features/home/room/detail/timeline/action/ViewEditHistoryViewModel.kt
index bda46d46..576ef5e9 100644
--- a/vector/src/main/java/im/vector/riotx/features/home/room/detail/timeline/action/ViewEditHistoryViewModel.kt
+++ b/vector/src/main/java/im/vector/riotx/features/home/room/detail/timeline/action/ViewEditHistoryViewModel.kt
@@ -23,6 +23,7 @@ import im.vector.matrix.android.api.session.Session
 import im.vector.matrix.android.api.session.events.model.Event
 import im.vector.matrix.android.api.session.events.model.toModel
 import im.vector.matrix.android.api.session.room.model.message.MessageContent
+import im.vector.matrix.android.api.session.room.model.message.isReply
 import im.vector.riotx.core.platform.VectorViewModel
 import im.vector.riotx.features.home.room.detail.timeline.helper.TimelineDateFormatter
 
@@ -83,7 +84,7 @@ class ViewEditHistoryViewModel @AssistedInject constructor(@Assisted
                 var originalIsReply = false
                 room.getTimeLineEvent(eventId)?.let {
                     withOriginal.add(it.root)
-                    originalIsReply = it.root.getClearContent().toModel<MessageContent>()?.relatesTo?.inReplyTo?.eventId != null
+                    originalIsReply = it.root.getClearContent().toModel<MessageContent>().isReply()
                 }
                 setState {
                     copy(