diff --git a/crates/matrix-sdk-crypto/src/olm/group_sessions/sender_data.rs b/crates/matrix-sdk-crypto/src/olm/group_sessions/sender_data.rs
index 098299d214e..309a11c3152 100644
--- a/crates/matrix-sdk-crypto/src/olm/group_sessions/sender_data.rs
+++ b/crates/matrix-sdk-crypto/src/olm/group_sessions/sender_data.rs
@@ -12,7 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-use ruma::{MilliSecondsSinceUnixEpoch, OwnedUserId};
+use ruma::{MilliSecondsSinceUnixEpoch, OwnedDeviceId, OwnedUserId};
 use serde::{Deserialize, Serialize};
 use vodozemac::Ed25519PublicKey;
 
@@ -66,6 +66,11 @@ pub enum SenderData {
         /// The user ID of the user who established this session.
         user_id: OwnedUserId,
 
+        /// The device ID of the device that send the session.
+        /// This is an `Option` for backwards compatibility, but we should
+        /// always populate it on creation.
+        device_id: Option<OwnedDeviceId>,
+
         /// The cross-signing key of the user who established this session.
         master_key: Ed25519PublicKey,
 
@@ -201,4 +206,22 @@ mod tests {
         let end: SenderData = serde_json::from_str(&json).unwrap();
         assert_eq!(start, end);
     }
+
+    #[test]
+    fn deserializing_senderknown_without_device_id_defaults_to_none() {
+        let json = r#"
+            {
+                "SenderKnown":{
+                    "user_id":"@u:s.co",
+                    "master_key":[
+                        150,140,249,139,141,29,63,230,179,14,213,175,176,61,11,255,
+                        26,103,10,51,100,154,183,47,181,117,87,204,33,215,241,92
+                    ],
+                    "master_key_verified":true
+                }
+            }
+            "#;
+
+        let _end: SenderData = serde_json::from_str(&json).expect("Failed to parse!");
+    }
 }
diff --git a/crates/matrix-sdk-crypto/src/olm/group_sessions/sender_data_finder.rs b/crates/matrix-sdk-crypto/src/olm/group_sessions/sender_data_finder.rs
index ed535e879ad..581aaa77013 100644
--- a/crates/matrix-sdk-crypto/src/olm/group_sessions/sender_data_finder.rs
+++ b/crates/matrix-sdk-crypto/src/olm/group_sessions/sender_data_finder.rs
@@ -257,6 +257,7 @@ impl<'a> SenderDataFinder<'a> {
     fn device_is_cross_signed_by_sender(&self, sender_device: Device) -> SenderData {
         // H (cross-signing key matches that used to sign the device!)
         let user_id = sender_device.user_id().to_owned();
+        let device_id = Some(sender_device.device_id().to_owned());
 
         let master_key = sender_device
             .device_owner_identity
@@ -266,7 +267,7 @@ impl<'a> SenderDataFinder<'a> {
         if let Some(master_key) = master_key {
             // We have user_id and master_key for the user sending the to-device message.
             let master_key_verified = sender_device.is_cross_signing_trusted();
-            SenderData::SenderKnown { user_id, master_key, master_key_verified }
+            SenderData::SenderKnown { user_id, device_id, master_key, master_key_verified }
         } else {
             // Surprisingly, there was no key in the MasterPubkey. We did not expect this:
             // treat it as if the device was not signed by this master key.
@@ -442,9 +443,11 @@ mod tests {
 
         // Then we get back the information about the sender
         assert_let!(
-            SenderData::SenderKnown { user_id, master_key, master_key_verified } = sender_data
+            SenderData::SenderKnown { user_id, device_id, master_key, master_key_verified } =
+                sender_data
         );
         assert_eq!(user_id, setup.sender.user_id);
+        assert_eq!(device_id.unwrap(), setup.sender_device.device_id());
         assert_eq!(master_key, setup.sender_master_key());
         assert!(!master_key_verified);
     }
@@ -469,9 +472,11 @@ mod tests {
 
         // Then we get back the information about the sender
         assert_let!(
-            SenderData::SenderKnown { user_id, master_key, master_key_verified } = sender_data
+            SenderData::SenderKnown { user_id, device_id, master_key, master_key_verified } =
+                sender_data
         );
         assert_eq!(user_id, setup.sender.user_id);
+        assert_eq!(device_id.unwrap(), setup.sender_device.device_id());
         assert_eq!(master_key, setup.sender_master_key());
         assert!(!master_key_verified);
     }
@@ -497,9 +502,11 @@ mod tests {
 
         // Then we get back the information about the sender
         assert_let!(
-            SenderData::SenderKnown { user_id, master_key, master_key_verified } = sender_data
+            SenderData::SenderKnown { user_id, device_id, master_key, master_key_verified } =
+                sender_data
         );
         assert_eq!(user_id, setup.sender.user_id);
+        assert_eq!(device_id.unwrap(), setup.sender_device.device_id());
         assert_eq!(master_key, setup.sender_master_key());
         assert!(!master_key_verified);
     }
@@ -524,9 +531,11 @@ mod tests {
 
         // Then we get back the information about the sender
         assert_let!(
-            SenderData::SenderKnown { user_id, master_key, master_key_verified } = sender_data
+            SenderData::SenderKnown { user_id, device_id, master_key, master_key_verified } =
+                sender_data
         );
         assert_eq!(user_id, setup.sender.user_id);
+        assert_eq!(device_id.unwrap(), setup.sender_device.device_id());
         assert_eq!(master_key, setup.sender_master_key());
         assert!(!master_key_verified);
     }
@@ -590,9 +599,11 @@ mod tests {
 
         // Then we get back the information about the sender
         assert_let!(
-            SenderData::SenderKnown { user_id, master_key, master_key_verified } = sender_data
+            SenderData::SenderKnown { user_id, device_id, master_key, master_key_verified } =
+                sender_data
         );
         assert_eq!(user_id, setup.sender.user_id);
+        assert_eq!(device_id.unwrap(), setup.sender_device.device_id());
         assert_eq!(master_key, setup.sender_master_key());
         // Including the fact that it was verified
         assert!(master_key_verified);
@@ -621,9 +632,11 @@ mod tests {
 
         // Then we get back the information about the sender
         assert_let!(
-            SenderData::SenderKnown { user_id, master_key, master_key_verified } = sender_data
+            SenderData::SenderKnown { user_id, device_id, master_key, master_key_verified } =
+                sender_data
         );
         assert_eq!(user_id, setup.sender.user_id);
+        assert_eq!(device_id.unwrap(), setup.sender_device.device_id());
         assert_eq!(master_key, setup.sender_master_key());
         // Including the fact that it was verified
         assert!(master_key_verified);
@@ -643,9 +656,11 @@ mod tests {
 
         // Then it is found using the device we supplied
         assert_let!(
-            SenderData::SenderKnown { user_id, master_key, master_key_verified } = sender_data
+            SenderData::SenderKnown { user_id, device_id, master_key, master_key_verified } =
+                sender_data
         );
         assert_eq!(user_id, setup.sender.user_id);
+        assert_eq!(device_id.unwrap(), setup.sender_device.device_id());
         assert_eq!(master_key, setup.sender_master_key());
         assert!(!master_key_verified);
     }