diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 3fc751ca..4de6b1ba 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -17,7 +17,7 @@ coverage:
     - sed -i s/#//g pubspec.yaml
     - flutter doctor
     - apt update
-    - apt install -y chromium lcov libolm3 sqlite3 libsqlite3-dev
+    - apt install -y chromium-bsu lcov libolm3 sqlite3 libsqlite3-dev
     - ln -s /usr/lib/dart/bin/pub /usr/bin/
     - useradd -m test
     - chown -R 'test:' '.'
@@ -62,7 +62,7 @@ e2ee_test:
     - curl https://dl-ssl.google.com/linux/linux_signing_key.pub | apt-key add -
     - curl https://storage.googleapis.com/download.dartlang.org/linux/debian/dart_stable.list > /etc/apt/sources.list.d/dart_stable.list
     - apt update
-    - apt install -y dart chromium lcov libolm3 sqlite3 libsqlite3-dev
+    - apt install -y dart chromium-bsu lcov libolm3 sqlite3 libsqlite3-dev
     - ln -s /usr/lib/dart/bin/pub /usr/bin/
     - useradd -m test
     - chown -R 'test:' '.'
diff --git a/lib/src/utils/device_keys_list.dart b/lib/src/utils/device_keys_list.dart
index 93ab0d49..83b3d0ed 100644
--- a/lib/src/utils/device_keys_list.dart
+++ b/lib/src/utils/device_keys_list.dart
@@ -184,6 +184,7 @@ abstract class SignableKey extends MatrixSignableKey {
       return false; // prevent recursion & validate hasValidSignatureChain
     }
     visited.add(setKey);
+    if (signatures == null) return false;
     for (final signatureEntries in signatures.entries) {
       final otherUserId = signatureEntries.key;
       if (!(signatureEntries.value is Map) ||