diff --git a/matrix_sdk_crypto/src/key_request.rs b/matrix_sdk_crypto/src/key_request.rs
index 67618038..3319e5dc 100644
--- a/matrix_sdk_crypto/src/key_request.rs
+++ b/matrix_sdk_crypto/src/key_request.rs
@@ -20,7 +20,7 @@
 // If we don't trust the device store an object that remembers the request and
 // let the users introspect that object.
 
-use dashmap::DashMap;
+use dashmap::{DashMap, DashSet};
 use serde::{Deserialize, Serialize};
 use serde_json::value::to_raw_value;
 use std::{collections::BTreeMap, sync::Arc};
@@ -34,13 +34,13 @@ use matrix_sdk_common::{
         room_key_request::{Action, RequestedKeyInfo, RoomKeyRequestEventContent},
         AnyToDeviceEvent, EventType, ToDeviceEvent,
     },
-    identifiers::{DeviceIdBox, EventEncryptionAlgorithm, RoomId, UserId},
+    identifiers::{DeviceId, DeviceIdBox, EventEncryptionAlgorithm, RoomId, UserId},
     uuid::Uuid,
     Raw,
 };
 
 use crate::{
-    error::OlmResult,
+    error::{OlmError, OlmResult},
     olm::{InboundGroupSession, OutboundGroupSession},
     requests::{OutgoingRequest, ToDeviceRequest},
     store::{CryptoStoreError, Store},
@@ -72,6 +72,10 @@ pub(crate) struct KeyRequestMachine {
     outgoing_to_device_requests: Arc<DashMap<Uuid, OutgoingRequest>>,
     incoming_key_requests:
         Arc<DashMap<(UserId, DeviceIdBox, String), ToDeviceEvent<RoomKeyRequestEventContent>>>,
+    requests_waiting_for_session:
+        Arc<DashMap<(UserId, DeviceIdBox, String), ToDeviceEvent<RoomKeyRequestEventContent>>>,
+    requests_ids_waiting: Arc<DashMap<(UserId, DeviceIdBox), DashSet<String>>>,
+    users_for_key_claim: Arc<DashMap<UserId, DashSet<DeviceIdBox>>>,
 }
 
 #[derive(Debug, Serialize, Deserialize)]
@@ -142,6 +146,9 @@ impl KeyRequestMachine {
             outbound_group_sessions,
             outgoing_to_device_requests: Arc::new(DashMap::new()),
             incoming_key_requests: Arc::new(DashMap::new()),
+            requests_waiting_for_session: Arc::new(DashMap::new()),
+            users_for_key_claim: Arc::new(DashMap::new()),
+            requests_ids_waiting: Arc::new(DashMap::new()),
         }
     }
 
@@ -163,6 +170,7 @@ impl KeyRequestMachine {
         let sender = event.sender.clone();
         let device_id = event.content.requesting_device_id.clone();
         let request_id = event.content.request_id.clone();
+
         self.incoming_key_requests
             .insert((sender, device_id, request_id), event.clone());
     }
@@ -180,6 +188,50 @@ impl KeyRequestMachine {
         Ok(())
     }
 
+    fn handle_key_share_without_session(
+        &self,
+        device: Device,
+        event: &ToDeviceEvent<RoomKeyRequestEventContent>,
+    ) {
+        self.users_for_key_claim
+            .entry(device.user_id().to_owned())
+            .or_insert_with(DashSet::new)
+            .insert(device.device_id().into());
+        let key = (
+            device.user_id().to_owned(),
+            device.device_id().into(),
+            event.content.request_id.to_owned(),
+        );
+        self.requests_waiting_for_session.insert(key, event.clone());
+    }
+
+    /// Retry keyshares for a device that previously didn't have an Olm session
+    /// with us.
+    ///
+    /// # Arguments
+    ///
+    /// * `user_id` - The user id of the device that we created the Olm session
+    /// with.
+    ///
+    /// * `device_id` - The device id of the device that got the Olm session.
+    pub fn retry_keyshare(&self, user_id: &UserId, device_id: &DeviceId) {
+        if let Some((_, request_ids)) = self
+            .requests_ids_waiting
+            .remove(&(user_id.to_owned(), device_id.into()))
+        {
+            for id in request_ids {
+                let key = (user_id.to_owned(), device_id.into(), id.to_owned());
+                let content = self.requests_waiting_for_session.remove(&key);
+
+                if let Some((_, c)) = content {
+                    if !self.incoming_key_requests.contains_key(&key) {
+                        self.incoming_key_requests.insert(key, c);
+                    }
+                }
+            }
+        }
+    }
+
     /// Handle a single incoming key request.
     #[instrument]
     async fn handle_key_request(
@@ -248,8 +300,15 @@ impl KeyRequestMachine {
                     device.device_id()
                 );
 
-                // TODO the missing session error here.
-                self.share_session(session, device).await?;
+                if let Err(e) = self.share_session(&session, &device).await {
+                    match e {
+                        OlmError::MissingSession => {
+                            self.handle_key_share_without_session(device, event);
+                            return Ok(());
+                        }
+                        e => return Err(e.into()),
+                    }
+                }
             }
         } else {
             warn!(
@@ -262,8 +321,8 @@ impl KeyRequestMachine {
         Ok(())
     }
 
-    async fn share_session(&self, session: InboundGroupSession, device: Device) -> OlmResult<()> {
-        let content = device.encrypt_session(session).await?;
+    async fn share_session(&self, session: &InboundGroupSession, device: &Device) -> OlmResult<()> {
+        let content = device.encrypt_session(session.clone()).await?;
 
         let id = Uuid::new_v4();
         let mut messages = BTreeMap::new();
diff --git a/matrix_sdk_crypto/src/machine.rs b/matrix_sdk_crypto/src/machine.rs
index d2b5bf49..fca75050 100644
--- a/matrix_sdk_crypto/src/machine.rs
+++ b/matrix_sdk_crypto/src/machine.rs
@@ -466,8 +466,7 @@ impl OlmMachine {
 
                 // TODO if this session was created because a previous one was
                 // wedged queue up a dummy event to be sent out.
-                // TODO if this session was created because of a key request,
-                // mark the forwarding keys to be sent out
+                self.key_request_machine.retry_keyshare(&user_id, device_id);
             }
         }
         Ok(())