diff --git a/src/backend/InvenTree/common/serializers.py b/src/backend/InvenTree/common/serializers.py
index 8b2e55c0142..3f769f618db 100644
--- a/src/backend/InvenTree/common/serializers.py
+++ b/src/backend/InvenTree/common/serializers.py
@@ -546,6 +546,10 @@ def save(self):
 
         model_type = self.validated_data.get('model_type', None)
 
+        # If the model type is not specified, attempt to infer it from the instance
+        if model_type is None and self.instance:
+            model_type = self.instance.model_type
+
         # Ensure that the user has permission to attach files to the specified model
         user = self.context.get('request').user