diff --git a/django_etebase/serializers.py b/django_etebase/serializers.py
index f78cd6b..f2da771 100644
--- a/django_etebase/serializers.py
+++ b/django_etebase/serializers.py
@@ -122,7 +122,7 @@ class CollectionItemRevisionSerializer(serializers.ModelSerializer):
 
 
 class CollectionItemSerializer(serializers.ModelSerializer):
-    encryptionKey = BinaryBase64Field(required=False, default=None)
+    encryptionKey = BinaryBase64Field(required=False, default=None, allow_null=True)
     etag = serializers.CharField(allow_null=True, write_only=True)
     content = CollectionItemRevisionSerializer(many=False)
 
@@ -192,7 +192,7 @@ class CollectionSerializer(serializers.ModelSerializer):
     stoken = serializers.CharField(read_only=True)
 
     uid = serializers.CharField(source='main_item.uid')
-    encryptionKey = BinaryBase64Field(source='main_item.encryptionKey', required=False, default=None)
+    encryptionKey = BinaryBase64Field(source='main_item.encryptionKey', required=False, default=None, allow_null=True)
     etag = serializers.CharField(allow_null=True, write_only=True)
     version = serializers.IntegerField(min_value=0, source='main_item.version')
     content = CollectionItemRevisionSerializer(many=False, source='main_item.content')