diff --git a/request_a_govuk_domain/request/middleware.py b/request_a_govuk_domain/request/middleware.py
index af3ec7df..ea87a625 100644
--- a/request_a_govuk_domain/request/middleware.py
+++ b/request_a_govuk_domain/request/middleware.py
@@ -22,28 +22,27 @@ def is_valid_start_path(self, path: str):
         return False
 
     def is_valid_progress(self, request):
+        if request.session.get("registration_data") is None:
+            return False
+        for key in request.session.get("registration_data"):
+            if key not in [
+                "applicant_email",
+                "applicant_name",
+                "applicant_phone",
+                "domain_name",
+                "domain_purpose",
+                "registrant_contact_email",
+                "registrant_contact_phone",
+                "registrant_email_address",
+                "registrant_full_name",
+                "registrant_organisation_name",
+                "registrant_phone",
+                "registrant_role",
+                "registrant_type",
+                "registrar_organisation",
+                "written_permission",
+            ]:
+                # A key in the session data is unknown. So go back to the beginning
+                request.session["registration_data"] = {}
+                return False
         return True
-        # if request.session.get("registration_data") is None:
-        #     return False
-        # for key in request.session.get("registration_data"):
-        #     if key not in [
-        #         "applicant_email",
-        #         "applicant_name",
-        #         "applicant_phone",
-        #         "domain_name",
-        #         "domain_purpose",
-        #         "registrant_contact_email",
-        #         "registrant_contact_phone",
-        #         "registrant_email_address",
-        #         "registrant_full_name",
-        #         "registrant_organisation_name",
-        #         "registrant_phone",
-        #         "registrant_role",
-        #         "registrant_type",
-        #         "registrar_organisation",
-        #         "written_permission",
-        #     ]:
-        #         # A key in the session data is invalid. So go back to the beginning
-        #         request.session["registration_data"] = {}
-        #         return False
-        # return True