diff --git a/matrix_sdk/src/client.rs b/matrix_sdk/src/client.rs
index 3cee36e2..ad1fc71a 100644
--- a/matrix_sdk/src/client.rs
+++ b/matrix_sdk/src/client.rs
@@ -105,7 +105,7 @@ use matrix_sdk_common::{
 #[cfg(feature = "encryption")]
 use matrix_sdk_common::{
     api::r0::{
-        keys::{claim_keys, get_keys, upload_keys},
+        keys::{get_keys, upload_keys},
         to_device::send_event_to_device::{
             Request as RumaToDeviceRequest, Response as ToDeviceResponse,
         },
@@ -143,6 +143,9 @@ pub struct Client {
     /// flight per room.
     #[cfg(feature = "encryption")]
     group_session_locks: DashMap<RoomId, Arc<Mutex<()>>>,
+    #[cfg(feature = "encryption")]
+    /// Lock making sure we're only doing one key claim request at a time.
+    key_claim_lock: Arc<Mutex<()>>,
 }
 
 #[cfg(not(tarpaulin_include))]
@@ -404,6 +407,8 @@ impl Client {
             base_client,
             #[cfg(feature = "encryption")]
             group_session_locks: DashMap::new(),
+            #[cfg(feature = "encryption")]
+            key_claim_lock: Arc::new(Mutex::new(())),
         })
     }
 
@@ -1017,19 +1022,16 @@ impl Client {
 
                 let _guard = mutex.lock().await;
 
-                let missing_sessions = {
+                {
                     let room = self.base_client.get_joined_room(room_id).await;
                     let room = room.as_ref().unwrap().read().await;
-                    let members = room
+                    let mut members = room
                         .joined_members
                         .keys()
                         .chain(room.invited_members.keys());
-                    self.base_client.get_missing_sessions(members).await?
+                    self.claim_one_time_keys(&mut members).await?;
                 };
 
-                if let Some((request_id, request)) = missing_sessions {
-                    self.claim_one_time_keys(&request_id, request).await?;
-                }
                 let response = self.share_group_session(room_id).await;
 
                 self.group_session_locks.remove(room_id);
@@ -1520,6 +1522,10 @@ impl Client {
 
             #[cfg(feature = "encryption")]
             {
+                if let Err(e) = self.claim_one_time_keys(&mut [].iter()).await {
+                    warn!("Error while claiming one-time keys {:?}", e);
+                }
+
                 for r in self.base_client.outgoing_requests().await {
                     match r.request() {
                         OutgoingRequests::KeysQuery(request) => {
@@ -1582,23 +1588,20 @@ impl Client {
     ///
     /// * `users` - The list of user/device pairs that we should claim keys for.
     ///
-    /// # Panics
-    ///
-    /// Panics if the client isn't logged in, or if no encryption keys need to
-    /// be uploaded.
     #[cfg(feature = "encryption")]
     #[cfg_attr(feature = "docs", doc(cfg(encryption)))]
-    #[instrument]
-    async fn claim_one_time_keys(
-        &self,
-        request_id: &Uuid,
-        request: claim_keys::Request,
-    ) -> Result<claim_keys::Response> {
-        let response = self.send(request).await?;
-        self.base_client
-            .mark_request_as_sent(request_id, &response)
-            .await?;
-        Ok(response)
+    #[instrument(skip(users))]
+    async fn claim_one_time_keys(&self, users: &mut impl Iterator<Item = &UserId>) -> Result<()> {
+        let _lock = self.key_claim_lock.lock().await;
+
+        if let Some((request_id, request)) = self.base_client.get_missing_sessions(users).await? {
+            let response = self.send(request).await?;
+            self.base_client
+                .mark_request_as_sent(&request_id, &response)
+                .await?;
+        }
+
+        Ok(())
     }
 
     /// Share a group session for a room.
diff --git a/matrix_sdk_base/src/client.rs b/matrix_sdk_base/src/client.rs
index 9161e376..eb0ad8e1 100644
--- a/matrix_sdk_base/src/client.rs
+++ b/matrix_sdk_base/src/client.rs
@@ -1291,7 +1291,7 @@ impl BaseClient {
     #[cfg_attr(feature = "docs", doc(cfg(encryption)))]
     pub async fn get_missing_sessions(
         &self,
-        users: impl Iterator<Item = &UserId>,
+        users: &mut impl Iterator<Item = &UserId>,
     ) -> Result<Option<(Uuid, KeysClaimRequest)>> {
         let olm = self.olm.lock().await;
 
diff --git a/matrix_sdk_crypto/src/machine.rs b/matrix_sdk_crypto/src/machine.rs
index 90f1bb4d..931739ad 100644
--- a/matrix_sdk_crypto/src/machine.rs
+++ b/matrix_sdk_crypto/src/machine.rs
@@ -379,7 +379,7 @@ impl OlmMachine {
     /// [`mark_request_as_sent`]: #method.mark_request_as_sent
     pub async fn get_missing_sessions(
         &self,
-        users: impl Iterator<Item = &UserId>,
+        users: &mut impl Iterator<Item = &UserId>,
     ) -> OlmResult<Option<(Uuid, KeysClaimRequest)>> {
         let mut missing = BTreeMap::new();
 
@@ -1456,7 +1456,7 @@ pub(crate) mod test {
         let alice_device = alice_device_id();
 
         let (_, missing_sessions) = machine
-            .get_missing_sessions([alice.clone()].iter())
+            .get_missing_sessions(&mut [alice.clone()].iter())
             .await
             .unwrap()
             .unwrap();