diff --git a/crates/matrix-sdk/src/client/mod.rs b/crates/matrix-sdk/src/client/mod.rs
index b9461c8f4df..a56c9ace993 100644
--- a/crates/matrix-sdk/src/client/mod.rs
+++ b/crates/matrix-sdk/src/client/mod.rs
@@ -777,7 +777,7 @@ impl Client {
     /// ```
     pub fn add_event_handler<Ev, Ctx, H>(&self, handler: H) -> EventHandlerHandle
     where
-        Ev: SyncEvent + DeserializeOwned + Send + 'static,
+        Ev: SyncEvent + DeserializeOwned + SendOutsideWasm + 'static,
         H: EventHandler<Ev, Ctx>,
     {
         self.add_event_handler_impl(handler, None)
@@ -799,7 +799,7 @@ impl Client {
         handler: H,
     ) -> EventHandlerHandle
     where
-        Ev: SyncEvent + DeserializeOwned + Send + 'static,
+        Ev: SyncEvent + DeserializeOwned + SendOutsideWasm + 'static,
         H: EventHandler<Ev, Ctx>,
     {
         self.add_event_handler_impl(handler, Some(room_id.to_owned()))
@@ -839,8 +839,8 @@ impl Client {
     /// [`EventHandlerSubscriber`]: crate::event_handler::EventHandlerSubscriber
     pub fn observe_events<Ev, Ctx>(&self) -> ObservableEventHandler<(Ev, Ctx)>
     where
-        Ev: SyncEvent + DeserializeOwned + Send + Sync + 'static,
-        Ctx: EventHandlerContext + Send + Sync + 'static,
+        Ev: SyncEvent + DeserializeOwned + SendOutsideWasm + SyncOutsideWasm + 'static,
+        Ctx: EventHandlerContext + SendOutsideWasm + SyncOutsideWasm + 'static,
     {
         self.observe_room_events_impl(None)
     }
@@ -856,8 +856,8 @@ impl Client {
         room_id: &RoomId,
     ) -> ObservableEventHandler<(Ev, Ctx)>
     where
-        Ev: SyncEvent + DeserializeOwned + Send + Sync + 'static,
-        Ctx: EventHandlerContext + Send + Sync + 'static,
+        Ev: SyncEvent + DeserializeOwned + SendOutsideWasm + SyncOutsideWasm + 'static,
+        Ctx: EventHandlerContext + SendOutsideWasm + SyncOutsideWasm + 'static,
     {
         self.observe_room_events_impl(Some(room_id.to_owned()))
     }
@@ -869,8 +869,8 @@ impl Client {
         room_id: Option<OwnedRoomId>,
     ) -> ObservableEventHandler<(Ev, Ctx)>
     where
-        Ev: SyncEvent + DeserializeOwned + Send + Sync + 'static,
-        Ctx: EventHandlerContext + Send + Sync + 'static,
+        Ev: SyncEvent + DeserializeOwned + SendOutsideWasm + SyncOutsideWasm + 'static,
+        Ctx: EventHandlerContext + SendOutsideWasm + SyncOutsideWasm + 'static,
     {
         // The default value is `None`. It becomes `Some((Ev, Ctx))` once it has a
         // new value.
diff --git a/crates/matrix-sdk/src/event_handler/mod.rs b/crates/matrix-sdk/src/event_handler/mod.rs
index 8d33139ed35..83bffe2559f 100644
--- a/crates/matrix-sdk/src/event_handler/mod.rs
+++ b/crates/matrix-sdk/src/event_handler/mod.rs
@@ -291,7 +291,7 @@ impl Client {
         room_id: Option<OwnedRoomId>,
     ) -> EventHandlerHandle
     where
-        Ev: SyncEvent + DeserializeOwned + Send + 'static,
+        Ev: SyncEvent + DeserializeOwned + SendOutsideWasm + 'static,
         H: EventHandler<Ev, Ctx>,
     {
         let handler_fn: Box<EventHandlerFn> = Box::new(move |data| {