diff --git a/CHANGES b/CHANGES
index ccdd626..539f6f3 100644
--- a/CHANGES
+++ b/CHANGES
@@ -3,6 +3,8 @@ Changes
 
 unreleased
 ------
+- fix Server error on saving StudyMedication and Adherence CRF proxy
+  models (#711)
 - add Gunicorn and Nginx web config
 - add project (static HTML) landing pages
 
diff --git a/effect_subject/reference_model_configs.py b/effect_subject/reference_model_configs.py
index bc7f667..a62dfa3 100644
--- a/effect_subject/reference_model_configs.py
+++ b/effect_subject/reference_model_configs.py
@@ -1,9 +1,25 @@
-from edc_reference import site_reference_configs
+from edc_reference import ReferenceModelConfig, site_reference_configs
 
 site_reference_configs.register_from_visit_schedule(
     visit_models={"edc_appointment.appointment": "effect_subject.subjectvisit"}
 )
 
+# Register main Adherence model (only accessed via proxy models)
+site_reference_configs.register(
+    reference_config=ReferenceModelConfig(
+        "effect_subject.adherence",
+        fields=["report_datetime"],
+    )
+)
+
+# Register main Study Medication model (only accessed via proxy models)
+site_reference_configs.register(
+    reference_config=ReferenceModelConfig(
+        "effect_subject.studymedication",
+        fields=["report_datetime"],
+    )
+)
+
 site_reference_configs.add_fields_to_config(
     name="effect_subject.signsandsymptoms",
     fields=["xray_performed", "lp_performed", "urinary_lam_performed"],