diff --git a/src/client_server.rs b/src/client_server.rs
index 054a0bc..ab70b31 100644
--- a/src/client_server.rs
+++ b/src/client_server.rs
@@ -714,7 +714,7 @@ pub fn upload_keys_route(
 
     if let Some(device_keys) = &body.device_keys {
         db.users
-            .add_device_keys(user_id, device_id, device_keys)
+            .add_device_keys(user_id, device_id, device_keys, &db.globals)
             .unwrap();
     }
 
@@ -1640,7 +1640,18 @@ pub fn sync_route(
                 .map(|(_, v)| v)
                 .collect(),
         },
-        device_lists: Default::default(),
+        device_lists: if since != 0 {
+            Some(sync_events::DeviceLists {
+                changed: db
+                    .users
+                    .device_keys_changed(since)
+                    .map(|u| u.unwrap().to_string())
+                    .collect(), // TODO: use userids when ruma changes
+                left: Vec::new(), // TODO
+            })
+        } else {
+            None // TODO: left
+        },
         device_one_time_keys_count: Default::default(),
         to_device: sync_events::ToDevice {
             events: db
@@ -1762,10 +1773,6 @@ pub fn get_media_config_route() -> MatrixResult<get_media_config::Response> {
 #[options("/<_segments..>")]
 pub fn options_route(
     _segments: rocket::http::uri::Segments<'_>,
-) -> MatrixResult<create_message_event::Response> {
-    MatrixResult(Err(Error {
-        kind: ErrorKind::NotFound,
-        message: "".to_owned(),
-        status_code: http::StatusCode::OK,
-    }))
+) -> MatrixResult<send_event_to_device::Response> {
+    MatrixResult(Ok(send_event_to_device::Response))
 }
diff --git a/src/database.rs b/src/database.rs
index 4cdad87..77ea2f9 100644
--- a/src/database.rs
+++ b/src/database.rs
@@ -61,6 +61,7 @@ impl Database {
                 token_userdeviceid: db.open_tree("token_userdeviceid").unwrap(),
                 onetimekeyid_onetimekeys: db.open_tree("onetimekeyid_onetimekeys").unwrap(),
                 userdeviceid_devicekeys: db.open_tree("userdeviceid_devicekeys").unwrap(),
+                devicekeychangeid_userid: db.open_tree("devicekeychangeid_userid").unwrap(),
                 todeviceid_events: db.open_tree("todeviceid_events").unwrap(),
             },
             rooms: rooms::Rooms {
diff --git a/src/database/users.rs b/src/database/users.rs
index ced5fe1..1b56066 100644
--- a/src/database/users.rs
+++ b/src/database/users.rs
@@ -15,6 +15,7 @@ pub struct Users {
 
     pub(super) onetimekeyid_onetimekeys: sled::Tree, // OneTimeKeyId = UserId + AlgorithmAndDeviceId
     pub(super) userdeviceid_devicekeys: sled::Tree,
+    pub(super) devicekeychangeid_userid: sled::Tree, // DeviceKeyChangeId = Count
 
     pub(super) todeviceid_events: sled::Tree, // ToDeviceId = UserId + DeviceId + Count
 }
@@ -259,6 +260,7 @@ impl Users {
         user_id: &UserId,
         device_id: &DeviceId,
         device_keys: &DeviceKeys,
+        globals: &super::globals::Globals,
     ) -> Result<()> {
         let mut userdeviceid = user_id.to_string().as_bytes().to_vec();
         userdeviceid.push(0xff);
@@ -267,6 +269,9 @@ impl Users {
         self.userdeviceid_devicekeys
             .insert(&userdeviceid, &*serde_json::to_string(&device_keys)?)?;
 
+        self.devicekeychangeid_userid
+            .insert(globals.next_count()?.to_be_bytes(), &*user_id.to_string())?;
+
         Ok(())
     }
 
@@ -285,6 +290,13 @@ impl Users {
             .map(|bytes| Ok(serde_json::from_slice(&bytes?)?))
     }
 
+    pub fn device_keys_changed(&self, since: u64) -> impl Iterator<Item = Result<UserId>> {
+        self.devicekeychangeid_userid
+            .range(since.to_be_bytes()..)
+            .values()
+            .map(|bytes| Ok(UserId::try_from(utils::string_from_bytes(&bytes?)?)?))
+    }
+
     pub fn all_device_keys(
         &self,
         user_id: &UserId,