diff --git a/bindings/matrix-sdk-ffi/src/timeline/mod.rs b/bindings/matrix-sdk-ffi/src/timeline/mod.rs
index 48859c77c..94c832897 100644
--- a/bindings/matrix-sdk-ffi/src/timeline/mod.rs
+++ b/bindings/matrix-sdk-ffi/src/timeline/mod.rs
@@ -746,8 +746,8 @@ impl TimelineItem {
         }
     }
 
-    pub fn unique_id(&self) -> u64 {
-        self.0.unique_id()
+    pub fn unique_id(&self) -> String {
+        self.0.unique_id().to_owned()
     }
 
     pub fn fmt_debug(&self) -> String {
diff --git a/crates/matrix-sdk-ui/src/timeline/day_dividers.rs b/crates/matrix-sdk-ui/src/timeline/day_dividers.rs
index 98b12ed7a..0c422ae98 100644
--- a/crates/matrix-sdk-ui/src/timeline/day_dividers.rs
+++ b/crates/matrix-sdk-ui/src/timeline/day_dividers.rs
@@ -291,7 +291,10 @@ impl DayDividerAdjuster {
                     }
 
                     let unique_id = replaced.unique_id();
-                    let item = TimelineItem::new(VirtualTimelineItem::DayDivider(ts), unique_id);
+                    let item = TimelineItem::new(
+                        VirtualTimelineItem::DayDivider(ts),
+                        unique_id.to_owned(),
+                    );
 
                     items.set(at, item);
                     max_i = i;
diff --git a/crates/matrix-sdk-ui/src/timeline/event_handler.rs b/crates/matrix-sdk-ui/src/timeline/event_handler.rs
index 5f009f85a..ce23b8509 100644
--- a/crates/matrix-sdk-ui/src/timeline/event_handler.rs
+++ b/crates/matrix-sdk-ui/src/timeline/event_handler.rs
@@ -934,13 +934,13 @@ impl<'a, 'o> TimelineEventHandler<'a, 'o> {
                         // If the old item is the last one and no day divider
                         // changes need to happen, replace and return early.
                         trace!(idx, "Replacing existing event");
-                        self.items.set(idx, TimelineItem::new(item, old_item_id));
+                        self.items.set(idx, TimelineItem::new(item, old_item_id.to_owned()));
                         return;
                     }
 
                     // In more complex cases, remove the item before re-adding the item.
                     trace!("Removing local echo or duplicate timeline item");
-                    removed_event_item_id = Some(self.items.remove(idx).internal_id);
+                    removed_event_item_id = Some(self.items.remove(idx).internal_id.clone());
 
                     // no return here, below code for adding a new event
                     // will run to re-add the removed item
@@ -988,7 +988,7 @@ impl<'a, 'o> TimelineEventHandler<'a, 'o> {
             #[cfg(feature = "e2e-encryption")]
             Flow::Remote { position: TimelineItemPosition::Update(idx), .. } => {
                 trace!("Updating timeline item at position {idx}");
-                let id = self.items[*idx].internal_id;
+                let id = self.items[*idx].internal_id.clone();
                 self.items.set(*idx, TimelineItem::new(item, id));
             }
         }
@@ -1040,7 +1040,7 @@ impl<'a, 'o> TimelineEventHandler<'a, 'o> {
             trace!("Found timeline item to update");
             if let Some(new_item) = update(self, item.inner) {
                 trace!("Updating item");
-                self.items.set(idx, TimelineItem::new(new_item, item.internal_id));
+                self.items.set(idx, TimelineItem::new(new_item, item.internal_id.to_owned()));
                 self.result.items_updated += 1;
             }
             true
diff --git a/crates/matrix-sdk-ui/src/timeline/inner/mod.rs b/crates/matrix-sdk-ui/src/timeline/inner/mod.rs
index 9731f7630..d78e38d84 100644
--- a/crates/matrix-sdk-ui/src/timeline/inner/mod.rs
+++ b/crates/matrix-sdk-ui/src/timeline/inner/mod.rs
@@ -1019,7 +1019,7 @@ impl TimelineInner {
         };
 
         trace!("Updating in-reply-to details");
-        let internal_id = item.internal_id;
+        let internal_id = item.internal_id.to_owned();
         let mut item = item.clone();
         item.set_content(TimelineItemContent::Message(
             message.with_in_reply_to(InReplyToDetails {
diff --git a/crates/matrix-sdk-ui/src/timeline/inner/state.rs b/crates/matrix-sdk-ui/src/timeline/inner/state.rs
index 1bfbeafb1..5618981a0 100644
--- a/crates/matrix-sdk-ui/src/timeline/inner/state.rs
+++ b/crates/matrix-sdk-ui/src/timeline/inner/state.rs
@@ -332,7 +332,7 @@ impl TimelineInnerState {
             }
         }
 
-        let item = TimelineItem::new(new_related, related.internal_id);
+        let item = TimelineItem::new(new_related, related.internal_id.to_owned());
         self.items.set(idx, item);
 
         Ok(())
@@ -757,10 +757,10 @@ impl TimelineInnerMetadata {
 
     /// Returns the next internal id for a timeline item (and increment our
     /// internal counter).
-    pub fn next_internal_id(&mut self) -> u64 {
+    pub fn next_internal_id(&mut self) -> String {
         let val = self.next_internal_id;
         self.next_internal_id += 1;
-        val
+        format!("{val}")
     }
 
     /// Returns a new timeline item with a fresh internal id.
diff --git a/crates/matrix-sdk-ui/src/timeline/item.rs b/crates/matrix-sdk-ui/src/timeline/item.rs
index 71fdba9a7..ba85a99ef 100644
--- a/crates/matrix-sdk-ui/src/timeline/item.rs
+++ b/crates/matrix-sdk-ui/src/timeline/item.rs
@@ -32,17 +32,18 @@ pub enum TimelineItemKind {
 #[derive(Clone, Debug)]
 pub struct TimelineItem {
     pub(crate) kind: TimelineItemKind,
-    pub(crate) internal_id: u64,
+    pub(crate) internal_id: String,
 }
 
 impl TimelineItem {
     /// Create a new `TimelineItem` with the given kind and internal id.
-    pub(crate) fn new(kind: impl Into<TimelineItemKind>, internal_id: u64) -> Arc<Self> {
+    pub(crate) fn new(kind: impl Into<TimelineItemKind>, internal_id: String) -> Arc<Self> {
         Arc::new(TimelineItem { kind: kind.into(), internal_id })
     }
 
+    /// Create a clone of the current `TimelineItem` with the given kind.
     pub(crate) fn with_kind(&self, kind: impl Into<TimelineItemKind>) -> Arc<Self> {
-        Arc::new(Self { kind: kind.into(), internal_id: self.internal_id })
+        Arc::new(Self { kind: kind.into(), internal_id: self.internal_id.clone() })
     }
 
     /// Get the [`TimelineItemKind`] of this item.
@@ -70,14 +71,14 @@ impl TimelineItem {
     /// dividers, identity isn't easy to define though and you might
     /// see a new ID getting generated for a day divider that you
     /// perceive to be "the same" as a previous one.
-    pub fn unique_id(&self) -> u64 {
-        self.internal_id
+    pub fn unique_id(&self) -> &str {
+        &self.internal_id
     }
 
     pub(crate) fn read_marker() -> Arc<TimelineItem> {
         Arc::new(Self {
             kind: TimelineItemKind::Virtual(VirtualTimelineItem::ReadMarker),
-            internal_id: u64::MAX,
+            internal_id: "__read_marker".to_owned(),
         })
     }
 
diff --git a/crates/matrix-sdk-ui/src/timeline/read_receipts.rs b/crates/matrix-sdk-ui/src/timeline/read_receipts.rs
index 9b26cbc27..f95013b05 100644
--- a/crates/matrix-sdk-ui/src/timeline/read_receipts.rs
+++ b/crates/matrix-sdk-ui/src/timeline/read_receipts.rs
@@ -286,7 +286,7 @@ impl ReadReceiptTimelineUpdate {
             return;
         };
 
-        let event_item_id = event_item.internal_id;
+        let event_item_id = event_item.internal_id.to_owned();
         let mut event_item = event_item.clone();
 
         if let Some(remote_event_item) = event_item.as_remote_mut() {
@@ -321,7 +321,7 @@ impl ReadReceiptTimelineUpdate {
             return;
         };
 
-        let event_item_id = event_item.internal_id;
+        let event_item_id = event_item.internal_id.to_owned();
         let mut event_item = event_item.clone();
 
         if let Some(remote_event_item) = event_item.as_remote_mut() {
@@ -468,7 +468,7 @@ impl TimelineInnerStateTransaction<'_> {
             return;
         };
 
-        let prev_event_item_id = prev_event_item.internal_id;
+        let prev_event_item_id = prev_event_item.internal_id.to_owned();
         let mut prev_event_item = prev_event_item.clone();
 
         let Some(remote_prev_event_item) = prev_event_item.as_remote_mut() else {
diff --git a/crates/matrix-sdk-ui/src/timeline/tests/basic.rs b/crates/matrix-sdk-ui/src/timeline/tests/basic.rs
index 293b32144..9afeb3ef6 100644
--- a/crates/matrix-sdk-ui/src/timeline/tests/basic.rs
+++ b/crates/matrix-sdk-ui/src/timeline/tests/basic.rs
@@ -316,10 +316,10 @@ async fn test_dedup_initial() {
     assert_eq!(event3.as_event().unwrap().sender(), *CAROL);
 
     // Make sure we reused IDs when deduplicating events
-    assert_eq!(event1.unique_id(), 0);
-    assert_eq!(event2.unique_id(), 1);
-    assert_eq!(event3.unique_id(), 2);
-    assert_eq!(timeline_items[0].unique_id(), 3);
+    assert_eq!(event1.unique_id(), "0");
+    assert_eq!(event2.unique_id(), "1");
+    assert_eq!(event3.unique_id(), "2");
+    assert_eq!(timeline_items[0].unique_id(), "3");
 }
 
 #[async_test]
diff --git a/crates/matrix-sdk-ui/src/timeline/tests/echo.rs b/crates/matrix-sdk-ui/src/timeline/tests/echo.rs
index 6622b7c4f..b3f096c3d 100644
--- a/crates/matrix-sdk-ui/src/timeline/tests/echo.rs
+++ b/crates/matrix-sdk-ui/src/timeline/tests/echo.rs
@@ -46,7 +46,7 @@ async fn test_remote_echo_full_trip() {
         assert!(event_item.is_local_echo());
         assert_matches!(event_item.send_state(), Some(EventSendState::NotSentYet));
         assert!(!event_item.can_be_replied_to());
-        item.unique_id()
+        item.unique_id().to_owned()
     };
 
     {
diff --git a/crates/matrix-sdk-ui/src/timeline/util.rs b/crates/matrix-sdk-ui/src/timeline/util.rs
index 4776446f8..49da7cd22 100644
--- a/crates/matrix-sdk-ui/src/timeline/util.rs
+++ b/crates/matrix-sdk-ui/src/timeline/util.rs
@@ -25,14 +25,14 @@ use super::{event_item::EventTimelineItemKind, EventTimelineItem, TimelineItem};
 pub(super) struct EventTimelineItemWithId<'a> {
     pub inner: &'a EventTimelineItem,
     /// Internal identifier generated by [`TimelineInnerMetadata`].
-    pub internal_id: u64,
+    pub internal_id: &'a str,
 }
 
 impl<'a> EventTimelineItemWithId<'a> {
     pub fn with_inner_kind(&self, kind: impl Into<EventTimelineItemKind>) -> Arc<TimelineItem> {
         Arc::new(TimelineItem {
             kind: self.inner.with_kind(kind).into(),
-            internal_id: self.internal_id,
+            internal_id: self.internal_id.to_owned(),
         })
     }
 }
@@ -59,7 +59,7 @@ pub(super) fn rfind_event_item(
         .filter_map(|(idx, item)| {
             Some((
                 idx,
-                EventTimelineItemWithId { inner: item.as_event()?, internal_id: item.internal_id },
+                EventTimelineItemWithId { inner: item.as_event()?, internal_id: &item.internal_id },
             ))
         })
         .rfind(|(_, it)| f(it.inner))