diff --git a/matrix_sdk_crypto/src/group_manager.rs b/matrix_sdk_crypto/src/group_manager.rs
index b9b070d8..d8391d50 100644
--- a/matrix_sdk_crypto/src/group_manager.rs
+++ b/matrix_sdk_crypto/src/group_manager.rs
@@ -12,13 +12,16 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-use std::{collections::BTreeMap, sync::Arc};
+use std::{
+    collections::{BTreeMap, HashSet},
+    sync::Arc,
+};
 
 use dashmap::DashMap;
 use matrix_sdk_common::{
     api::r0::to_device::DeviceIdOrAllDevices,
     events::{room::encrypted::EncryptedEventContent, AnyMessageEventContent, EventType},
-    identifiers::{RoomId, UserId},
+    identifiers::{DeviceId, RoomId, UserId},
     uuid::Uuid,
 };
 use tracing::debug;
@@ -30,7 +33,7 @@ use crate::{
     Device, EncryptionSettings, OlmError, ToDeviceRequest,
 };
 
-#[derive(Clone)]
+#[derive(Debug, Clone)]
 pub struct GroupSessionManager {
     account: Account,
     /// Store for the encryption keys.
@@ -64,6 +67,29 @@ impl GroupSessionManager {
         }
     }
 
+    pub fn invalidate_sessions_new_devices(&self, users: &HashSet<&UserId>) {
+        for session in self.outbound_group_sessions.iter() {
+            if users.iter().any(|u| session.contains_recipient(u)) {
+                session.invalidate_session()
+            }
+        }
+    }
+
+    /// Invalidate the sessions that were sent to the given user/device pair.
+    pub fn invalidate_sessions(&self, user_id: &UserId, device_id: &DeviceId) {
+        for session in self.outbound_group_sessions.iter() {
+            if session.is_shared_with(user_id, device_id) {
+                session.invalidate_session();
+
+                if !session.shared() {
+                    for request_id in session.clear_requests() {
+                        self.outbound_sessions_being_shared.remove(&request_id);
+                    }
+                }
+            }
+        }
+    }
+
     /// Get an outbound group session for a room, if one exists.
     ///
     /// # Arguments
@@ -105,7 +131,7 @@ impl GroupSessionManager {
         let session = self.outbound_group_sessions.get(room_id);
 
         match session {
-            Some(s) => !s.shared() || s.expired(),
+            Some(s) => !s.shared() || s.expired() || s.invalidated(),
             None => true,
         }
     }
@@ -158,6 +184,7 @@ impl GroupSessionManager {
         let mut devices: Vec<Device> = Vec::new();
 
         for user_id in users {
+            session.add_recipient(user_id);
             let user_devices = self.store.get_user_devices(&user_id).await?;
             devices.extend(user_devices.devices().filter(|d| !d.is_blacklisted()));
         }
diff --git a/matrix_sdk_crypto/src/identities/manager.rs b/matrix_sdk_crypto/src/identities/manager.rs
index 509c3269..99a13a4a 100644
--- a/matrix_sdk_crypto/src/identities/manager.rs
+++ b/matrix_sdk_crypto/src/identities/manager.rs
@@ -27,6 +27,7 @@ use matrix_sdk_common::{
 
 use crate::{
     error::OlmResult,
+    group_manager::GroupSessionManager,
     identities::{
         MasterPubkey, OwnUserIdentity, ReadOnlyDevice, SelfSigningPubkey, UserIdentities,
         UserIdentity, UserSigningPubkey,
@@ -39,15 +40,22 @@ use crate::{
 pub(crate) struct IdentityManager {
     user_id: Arc<UserId>,
     device_id: Arc<DeviceIdBox>,
+    group_manager: GroupSessionManager,
     store: Store,
 }
 
 impl IdentityManager {
-    pub fn new(user_id: Arc<UserId>, device_id: Arc<DeviceIdBox>, store: Store) -> Self {
+    pub fn new(
+        user_id: Arc<UserId>,
+        device_id: Arc<DeviceIdBox>,
+        store: Store,
+        group_manager: GroupSessionManager,
+    ) -> Self {
         IdentityManager {
             user_id,
             device_id,
             store,
+            group_manager,
         }
     }
 
@@ -104,6 +112,7 @@ impl IdentityManager {
         &self,
         device_keys_map: &BTreeMap<UserId, BTreeMap<DeviceIdBox, DeviceKeys>>,
     ) -> StoreResult<Vec<ReadOnlyDevice>> {
+        let mut users_with_new_devices = HashSet::new();
         let mut changed_devices = Vec::new();
 
         for (user_id, device_map) in device_keys_map {
@@ -149,6 +158,7 @@ impl IdentityManager {
                         }
                     };
                     info!("Adding a new device to the device store {:?}", device);
+                    users_with_new_devices.insert(user_id);
                     device
                 };
 
@@ -164,12 +174,17 @@ impl IdentityManager {
 
             for device_id in deleted_devices {
                 if let Some(device) = stored_devices.get(device_id) {
+                    self.group_manager
+                        .invalidate_sessions(device.user_id(), device.device_id());
                     device.mark_as_deleted();
                     self.store.delete_device(device).await?;
                 }
             }
         }
 
+        self.group_manager
+            .invalidate_sessions_new_devices(&users_with_new_devices);
+
         Ok(changed_devices)
     }
 
@@ -362,9 +377,10 @@ pub(crate) mod test {
     use serde_json::json;
 
     use crate::{
+        group_manager::GroupSessionManager,
         identities::IdentityManager,
         machine::test::response_from_file,
-        olm::ReadOnlyAccount,
+        olm::{Account, ReadOnlyAccount},
         store::{CryptoStore, MemoryStore, Store},
         verification::VerificationMachine,
     };
@@ -385,13 +401,18 @@ pub(crate) mod test {
         let user_id = Arc::new(user_id());
         let account = ReadOnlyAccount::new(&user_id, &device_id());
         let store: Arc<Box<dyn CryptoStore>> = Arc::new(Box::new(MemoryStore::new()));
-        let verification = VerificationMachine::new(account, store);
+        let verification = VerificationMachine::new(account.clone(), store);
         let store = Store::new(
             user_id.clone(),
             Arc::new(Box::new(MemoryStore::new())),
             verification,
         );
-        IdentityManager::new(user_id, Arc::new(device_id()), store)
+        let account = Account {
+            inner: account,
+            store: store.clone(),
+        };
+        let group = GroupSessionManager::new(account.clone(), store.clone());
+        IdentityManager::new(user_id, Arc::new(device_id()), store, group)
     }
 
     pub(crate) fn other_key_query() -> KeyQueryResponse {
diff --git a/matrix_sdk_crypto/src/machine.rs b/matrix_sdk_crypto/src/machine.rs
index 931739ad..757f053f 100644
--- a/matrix_sdk_crypto/src/machine.rs
+++ b/matrix_sdk_crypto/src/machine.rs
@@ -136,14 +136,19 @@ impl OlmMachine {
             store.clone(),
             outbound_group_sessions,
         );
-        let identity_manager =
-            IdentityManager::new(user_id.clone(), device_id.clone(), store.clone());
+
         let account = Account {
             inner: account,
             store: store.clone(),
         };
 
         let group_session_manager = GroupSessionManager::new(account.clone(), store.clone());
+        let identity_manager = IdentityManager::new(
+            user_id.clone(),
+            device_id.clone(),
+            store.clone(),
+            group_session_manager.clone(),
+        );
 
         OlmMachine {
             user_id,
diff --git a/matrix_sdk_crypto/src/olm/account.rs b/matrix_sdk_crypto/src/olm/account.rs
index 86a9dfa1..0cf5e569 100644
--- a/matrix_sdk_crypto/src/olm/account.rs
+++ b/matrix_sdk_crypto/src/olm/account.rs
@@ -58,7 +58,7 @@ use crate::{
 
 use super::{EncryptionSettings, InboundGroupSession, OutboundGroupSession, Session};
 
-#[derive(Clone)]
+#[derive(Debug, Clone)]
 pub struct Account {
     pub(crate) inner: ReadOnlyAccount,
     pub(crate) store: Store,
diff --git a/matrix_sdk_crypto/src/olm/group_sessions/outbound.rs b/matrix_sdk_crypto/src/olm/group_sessions/outbound.rs
index 54e59c53..d2daab7e 100644
--- a/matrix_sdk_crypto/src/olm/group_sessions/outbound.rs
+++ b/matrix_sdk_crypto/src/olm/group_sessions/outbound.rs
@@ -104,6 +104,7 @@ pub struct OutboundGroupSession {
     pub(crate) creation_time: Arc<Instant>,
     message_count: Arc<AtomicU64>,
     shared: Arc<AtomicBool>,
+    invalidated: Arc<AtomicBool>,
     settings: Arc<EncryptionSettings>,
     shared_with_set: Arc<DashMap<UserId, DashSet<DeviceIdBox>>>,
     to_share_with_set: Arc<DashMap<Uuid, Arc<ToDeviceRequest>>>,
@@ -143,6 +144,7 @@ impl OutboundGroupSession {
             creation_time: Arc::new(Instant::now()),
             message_count: Arc::new(AtomicU64::new(0)),
             shared: Arc::new(AtomicBool::new(false)),
+            invalidated: Arc::new(AtomicBool::new(false)),
             settings: Arc::new(settings),
             shared_with_set: Arc::new(DashMap::new()),
             to_share_with_set: Arc::new(DashMap::new()),
@@ -153,6 +155,16 @@ impl OutboundGroupSession {
         self.to_share_with_set.insert(request_id, request);
     }
 
+    pub fn add_recipient(&self, user_id: &UserId) {
+        self.shared_with_set
+            .entry(user_id.to_owned())
+            .or_insert_with(DashSet::new);
+    }
+
+    pub fn contains_recipient(&self, user_id: &UserId) -> bool {
+        self.shared_with_set.contains_key(user_id)
+    }
+
     /// Mark the request with the given request id as sent.
     ///
     /// This removes the request from the queue and marks the set of
@@ -263,6 +275,11 @@ impl OutboundGroupSession {
                 >= min(self.settings.rotation_period, Duration::from_secs(3600))
     }
 
+    /// Has the session been invalidated.
+    pub fn invalidated(&self) -> bool {
+        self.invalidated.load(Ordering::Relaxed)
+    }
+
     /// Mark the session as shared.
     ///
     /// Messages shouldn't be encrypted with the session before it has been
@@ -315,12 +332,48 @@ impl OutboundGroupSession {
         })
     }
 
-    /// The set of users this session is shared with.
+    /// Mark the session as invalid.
+    ///
+    /// This should be called if an user/device deletes a device that received
+    /// this session.
+    pub fn invalidate_session(&self) {
+        self.invalidated.store(true, Ordering::Relaxed)
+    }
+
+    /// Clear out the requests returning the request ids.
+    pub fn clear_requests(&self) -> Vec<Uuid> {
+        let request_ids = self
+            .to_share_with_set
+            .iter()
+            .map(|item| *item.key())
+            .collect();
+        self.to_share_with_set.clear();
+        request_ids
+    }
+
+    /// Has or will the session be shared with the given user/device pair.
     pub(crate) fn is_shared_with(&self, user_id: &UserId, device_id: &DeviceId) -> bool {
-        self.shared_with_set
+        let shared_with = self
+            .shared_with_set
             .get(user_id)
             .map(|d| d.contains(device_id))
-            .unwrap_or(false)
+            .unwrap_or(false);
+
+        let should_be_shared_with = if self.shared() {
+            false
+        } else {
+            let device_id = DeviceIdOrAllDevices::DeviceId(device_id.into());
+
+            self.to_share_with_set.iter().any(|item| {
+                if let Some(e) = item.value().messages.get(user_id) {
+                    e.contains_key(&device_id)
+                } else {
+                    false
+                }
+            })
+        };
+
+        shared_with || should_be_shared_with
     }
 
     /// Mark that the session was shared with the given user/device pair.