diff --git a/crates/matrix-sdk-crypto/src/identities/device.rs b/crates/matrix-sdk-crypto/src/identities/device.rs
index d127c3cdf..430f5580d 100644
--- a/crates/matrix-sdk-crypto/src/identities/device.rs
+++ b/crates/matrix-sdk-crypto/src/identities/device.rs
@@ -60,8 +60,10 @@ use crate::{
 
 pub enum MaybeEncryptedRoomKey {
     Encrypted {
-        used_session: Session,
-        share_info: ShareInfo,
+        // `Box` the session to reduce the size of `Encrypted`.
+        used_session: Box<Session>,
+        // `Box` the session to reduce the size of `Encrypted`.
+        share_info: Box<ShareInfo>,
         message: Raw<AnyToDeviceEventContent>,
     },
     /// We could not encrypt a message to this device because there is no active
@@ -832,12 +834,12 @@ impl DeviceData {
 
         match self.encrypt(store, &event_type, content).await {
             Ok((session, encrypted)) => Ok(MaybeEncryptedRoomKey::Encrypted {
-                share_info: ShareInfo::new_shared(
+                share_info: Box::new(ShareInfo::new_shared(
                     session.sender_key().to_owned(),
                     message_index,
                     self.olm_wedging_index,
-                ),
-                used_session: session,
+                )),
+                used_session: Box::new(session),
                 message: encrypted.cast(),
             }),
 
diff --git a/crates/matrix-sdk-crypto/src/session_manager/group_sessions/mod.rs b/crates/matrix-sdk-crypto/src/session_manager/group_sessions/mod.rs
index 411930063..5a5a38969 100644
--- a/crates/matrix-sdk-crypto/src/session_manager/group_sessions/mod.rs
+++ b/crates/matrix-sdk-crypto/src/session_manager/group_sessions/mod.rs
@@ -310,14 +310,14 @@ impl GroupSessionManager {
 
             match result.maybe_encrypted_room_key {
                 MaybeEncryptedRoomKey::Encrypted { used_session, share_info, message } => {
-                    result_builder.on_successful_encryption(&result.device, used_session, message);
+                    result_builder.on_successful_encryption(&result.device, *used_session, message);
 
                     let user_id = result.device.user_id().to_owned();
                     let device_id = result.device.device_id().to_owned();
                     share_infos
                         .entry(user_id)
                         .or_insert_with(BTreeMap::new)
-                        .insert(device_id, share_info);
+                        .insert(device_id, *share_info);
                 }
                 MaybeEncryptedRoomKey::MissingSession => {
                     result_builder.on_missing_session(result.device);