diff --git a/tests/to_device.rs b/tests/to_device.rs
new file mode 100644
index 00000000..09d9a012
--- /dev/null
+++ b/tests/to_device.rs
@@ -0,0 +1,34 @@
+use std::convert::TryFrom;
+
+use ruma_events::{
+    room_key::RoomKeyEventContent, Algorithm, AnyToDeviceEventContent, ToDeviceEvent,
+};
+use ruma_identifiers::{RoomId, UserId};
+use serde_json::{json, to_value as to_json_value};
+
+#[test]
+fn serialization() {
+    let ev = ToDeviceEvent {
+        sender: UserId::try_from("@example:example.org").unwrap(),
+        content: AnyToDeviceEventContent::RoomKey(RoomKeyEventContent {
+            algorithm: Algorithm::MegolmV1AesSha2,
+            room_id: RoomId::try_from("!testroomid:example.org").unwrap(),
+            session_id: "SessId".into(),
+            session_key: "SessKey".into(),
+        }),
+    };
+
+    assert_eq!(
+        to_json_value(ev).unwrap(),
+        json!({
+            "type": "m.room_key",
+            "sender": "@example:example.org",
+            "content": {
+                "algorithm": "m.megolm.v1.aes-sha2",
+                "room_id": "!testroomid:example.org",
+                "session_id": "SessId",
+                "session_key": "SessKey",
+            },
+        })
+    );
+}