diff --git a/lib/encryption/cross_signing.dart b/lib/encryption/cross_signing.dart
index e4d8bc9..6154088 100644
--- a/lib/encryption/cross_signing.dart
+++ b/lib/encryption/cross_signing.dart
@@ -123,14 +123,8 @@ class CrossSigning {
       if (key == null || signedWith == null || signature == null) {
         return;
       }
-      final signedKey = signedKeys.firstWhere(
-              (k) => k.userId == key.userId && k.identifier == key.identifier,
-              orElse: () => null) ??
-          key.cloneForSigning();
-      signedKey.signatures ??= <String, Map<String, String>>{};
-      if (!signedKey.signatures.containsKey(signedWith.userId)) {
-        signedKey.signatures[signedWith.userId] = <String, String>{};
-      }
+      final signedKey = key.cloneForSigning();
+      signedKey.signatures[signedWith.userId] = <String, String>{};
       signedKey.signatures[signedWith.userId]
           ['ed25519:${signedWith.identifier}'] = signature;
       signedKeys.add(signedKey);
diff --git a/lib/src/utils/device_keys_list.dart b/lib/src/utils/device_keys_list.dart
index 27ee9f7..2159d51 100644
--- a/lib/src/utils/device_keys_list.dart
+++ b/lib/src/utils/device_keys_list.dart
@@ -125,6 +125,7 @@ abstract class SignableKey extends MatrixSignableKey {
   MatrixSignableKey cloneForSigning() {
     final newKey =
         MatrixSignableKey.fromJson(Map<String, dynamic>.from(toJson()));
+    newKey.signatures ??= <String, Map<String, String>>{};
     newKey.signatures.clear();
     return newKey;
   }