diff --git a/beat/web/common/serializers.py b/beat/web/common/serializers.py
index 3e32c53906e9f261f46fea29501c7a8af9e25e74..6e1a21bd13f0ed0c232630b170c19666082b41a8 100644
--- a/beat/web/common/serializers.py
+++ b/beat/web/common/serializers.py
@@ -364,7 +364,7 @@ class ContributionModSerializer(serializers.ModelSerializer):
 
 
 class ContributionCreationSerializer(ContributionModSerializer):
-    fork_of = serializers.JSONField(required=False)
+    fork_of = serializers.CharField(required=False)
     previous_version = serializers.CharField(required=False)
     version = serializers.IntegerField(min_value=1)