diff --git a/lib/src/omemo/ratchet_map_key.dart b/lib/src/omemo/ratchet_map_key.dart
new file mode 100644
index 0000000..d236724
--- /dev/null
+++ b/lib/src/omemo/ratchet_map_key.dart
@@ -0,0 +1,18 @@
+import 'package:meta/meta.dart';
+
+@internal
+@immutable
+class RatchetMapKey {
+
+  const RatchetMapKey(this.jid, this.deviceId);
+  final String jid;
+  final int deviceId;
+
+  @override
+  bool operator ==(Object other) {
+    return other is RatchetMapKey && jid == other.jid && deviceId == other.deviceId;
+  }
+
+  @override
+  int get hashCode => jid.hashCode ^ deviceId.hashCode;
+}
diff --git a/lib/src/omemo/sessionmanager.dart b/lib/src/omemo/sessionmanager.dart
index 13db63e..9419284 100644
--- a/lib/src/omemo/sessionmanager.dart
+++ b/lib/src/omemo/sessionmanager.dart
@@ -13,6 +13,7 @@ import 'package:omemo_dart/src/keys.dart';
 import 'package:omemo_dart/src/omemo/bundle.dart';
 import 'package:omemo_dart/src/omemo/device.dart';
 import 'package:omemo_dart/src/omemo/fingerprint.dart';
+import 'package:omemo_dart/src/omemo/ratchet_map_key.dart';
 import 'package:omemo_dart/src/protobuf/omemo_authenticated_message.dart';
 import 'package:omemo_dart/src/protobuf/omemo_key_exchange.dart';
 import 'package:omemo_dart/src/protobuf/omemo_message.dart';
@@ -43,22 +44,6 @@ class EncryptedKey {
   final bool kex;
 }
 
-@immutable
-class RatchetMapKey {
-
-  const RatchetMapKey(this.jid, this.deviceId);
-  final String jid;
-  final int deviceId;
-
-  @override
-  bool operator ==(Object other) {
-    return other is RatchetMapKey && jid == other.jid && deviceId == other.deviceId;
-  }
-
-  @override
-  int get hashCode => jid.hashCode ^ deviceId.hashCode;
-}
-
 class OmemoSessionManager {
 
   OmemoSessionManager(this._device, this._deviceMap, this._ratchetMap)