diff --git a/lib/src/event.dart b/lib/src/event.dart
index 154f090..45f9d03 100644
--- a/lib/src/event.dart
+++ b/lib/src/event.dart
@@ -93,9 +93,7 @@ class Event extends MatrixEvent {
     // into the unsigned block
     this.prevContent = prevContent != null && prevContent.isNotEmpty
         ? prevContent
-        : (unsigned != null &&
-                unsigned.containsKey('prev_content') &&
-                unsigned['prev_content'] is Map
+        : (unsigned != null && unsigned['prev_content'] is Map
             ? unsigned['prev_content']
             : null);
     this.stateKey = stateKey;
@@ -483,8 +481,7 @@ class Event extends MatrixEvent {
         final targetName = stateKeyUser.calcDisplayname();
         // Has the membership changed?
         final newMembership = content['membership'] ?? '';
-        final oldMembership = unsigned.containsKey('prev_content') &&
-                unsigned['prev_content'] is Map<String, dynamic>
+        final oldMembership = unsigned != null && unsigned['prev_content'] is Map<String, dynamic>
             ? unsigned['prev_content']['membership'] ?? ''
             : '';
         if (newMembership != oldMembership) {
@@ -521,14 +518,12 @@ class Event extends MatrixEvent {
           }
         } else if (newMembership == 'join') {
           final newAvatar = content['avatar_url'] ?? '';
-          final oldAvatar = unsigned.containsKey('prev_content') &&
-                  unsigned['prev_content'] is Map<String, dynamic>
+          final oldAvatar = unsigned != null && unsigned['prev_content'] is Map<String, dynamic>
               ? unsigned['prev_content']['avatar_url'] ?? ''
               : '';
 
           final newDisplayname = content['displayname'] ?? '';
-          final oldDisplayname = unsigned.containsKey('prev_content') &&
-                  unsigned['prev_content'] is Map<String, dynamic>
+          final oldDisplayname = unsigned != null && unsigned['prev_content'] is Map<String, dynamic>
               ? unsigned['prev_content']['displayname'] ?? ''
               : '';