diff --git a/src/staff/utils.ts b/src/staff/utils.ts
index 3a635af8b..70b65362e 100644
--- a/src/staff/utils.ts
+++ b/src/staff/utils.ts
@@ -7,9 +7,13 @@ import { StaffDetailsFormData } from "./components/StaffDetailsPage";
  * Return lists of groups which have to be added and removed from user.
  */
 export const groupsDiff = (
-  user: StaffMemberDetailsFragment,
+  user: StaffMemberDetailsFragment | undefined,
   formData: StaffDetailsFormData,
 ) => {
+  if (!user) {
+    return {};
+  }
+
   const newGroups = formData.permissionGroups;
   const oldGroups = user.permissionGroups.map(u => u.id);