diff --git a/lib/src/model/answer/answer_format.dart b/lib/src/model/answer/answer_format.dart
index c36c2411..7c789a8b 100644
--- a/lib/src/model/answer/answer_format.dart
+++ b/lib/src/model/answer/answer_format.dart
@@ -58,4 +58,10 @@ abstract class AnswerFormat {
         throw Exception('Unknown type: $type');
     }
   }
+
+  Map<String, dynamic> toJson() {
+    return {
+      'type': answerType,
+    };
+  }
 }
diff --git a/lib/src/model/content/content.dart b/lib/src/model/content/content.dart
index 7bf4d942..a561bd17 100644
--- a/lib/src/model/content/content.dart
+++ b/lib/src/model/content/content.dart
@@ -38,5 +38,12 @@ abstract class Content {
     }
   }
 
+  Map<String, dynamic> toJson() {
+    return {
+      'id': id,
+      'type': contentType,
+    };
+  }
+
   Widget createWidget();
 }