diff --git a/atlas/models.py b/atlas/models.py
index 5852fb4d..7e6ffe66 100644
--- a/atlas/models.py
+++ b/atlas/models.py
@@ -1243,7 +1243,7 @@ class CaseDetail(models.Model):
             for prior in self.case.prior_case.all():
                 case_series_images.extend(prior.get_series_images_nested(as_json=False))
 
-        return case_series_images
+        return json.dumps(case_series_images)
 
 
 class CasePrior(models.Model):