diff --git a/DigitalLearningSolutions.Data/DataServices/RegistrationDataService.cs b/DigitalLearningSolutions.Data/DataServices/RegistrationDataService.cs
index d6b229e721..ced09e50f3 100644
--- a/DigitalLearningSolutions.Data/DataServices/RegistrationDataService.cs
+++ b/DigitalLearningSolutions.Data/DataServices/RegistrationDataService.cs
@@ -197,7 +197,7 @@ public int RegisterAdmin(
                 isSupervisor = registrationModel.IsSupervisor,
                 isNominatedSupervisor = registrationModel.IsNominatedSupervisor,
             };
-
+            
             var adminUserId = connection.QuerySingle<int>(
                 @"INSERT INTO AdminAccounts
                     (
@@ -219,7 +219,10 @@ OUTPUT Inserted.ID
                     (
                         @userId,
                         @centreId,
-                        @categoryId,
+                        CASE 
+                        WHEN @categoryID = 0 THEN NULL 
+                        ELSE @categoryID 
+                        END,
                         @isCentreAdmin,
                         @isCentreManager,
                         @active,
diff --git a/DigitalLearningSolutions.Web/Controllers/SupervisorController/Supervisor.cs b/DigitalLearningSolutions.Web/Controllers/SupervisorController/Supervisor.cs
index e051d12737..11d8ab1e7d 100644
--- a/DigitalLearningSolutions.Web/Controllers/SupervisorController/Supervisor.cs
+++ b/DigitalLearningSolutions.Web/Controllers/SupervisorController/Supervisor.cs
@@ -1314,7 +1314,7 @@ public IActionResult ConfirmNominateSupervisor(SupervisorDelegateViewModel super
                     supervisorDelegateDetail.DelegateUserID,
                     (int)User.GetCentreId()
                 );
-                supervisorDelegate.SelfAssessmentCategory = supervisorDelegate.SelfAssessmentCategory == 0 ? adminUser.CategoryId.Value : supervisorDelegate.SelfAssessmentCategory;
+                supervisorDelegate.SelfAssessmentCategory = supervisorDelegate.SelfAssessmentCategory == 0 ? (adminUser.CategoryId.HasValue ? adminUser.CategoryId.Value : 0) : supervisorDelegate.SelfAssessmentCategory;
                 var centreName = adminUser.CentreName;
 
                 var adminRoles = new AdminRoles(false, false, true, false, false, false, false, false);