diff --git a/app/models/type/attribute_group.rb b/app/models/type/attribute_group.rb
index bc88702058d..7e9c16403e2 100644
--- a/app/models/type/attribute_group.rb
+++ b/app/models/type/attribute_group.rb
@@ -33,7 +33,7 @@ class Type::AttributeGroup < Type::FormGroup
     # The attributes might not be present anymore, for instance when you remove
     # a plugin leaving an empty group behind. If we did not delete such a
     # group, the admin saving such a form configuration would encounter an
-    # unexpected/unexplicable validation error.
+    # unexpected/inexplicable validation error.
     valid_keys = type.work_package_attributes.keys
 
     (attributes & valid_keys)
diff --git a/app/services/work_package_types/form_configuration/concern.rb b/app/services/work_package_types/form_configuration/concern.rb
index 765d736bf87..6734d189a97 100644
--- a/app/services/work_package_types/form_configuration/concern.rb
+++ b/app/services/work_package_types/form_configuration/concern.rb
@@ -106,7 +106,7 @@ module WorkPackageTypes
                  .reject { |group| group.key.to_s == "__empty" }
         seen_keys = groups.filter_map(&:key).compact_blank.map(&:to_s)
         groups = groups.map { |group| normalize_group(group, seen_keys:) }
-        groups = prune_unavailable_attribute_group_items(groups)
+        prune_unavailable_attribute_group_items(groups)
 
         if groups.empty?
           [::Type::AttributeGroup.new(type, :__empty, [])]
diff --git a/spec/services/work_package_types/form_configuration_rows/update_service_spec.rb b/spec/services/work_package_types/form_configuration_rows/update_service_spec.rb
index 1d9b3c90bb5..b1bfdc67915 100644
--- a/spec/services/work_package_types/form_configuration_rows/update_service_spec.rb
+++ b/spec/services/work_package_types/form_configuration_rows/update_service_spec.rb
@@ -71,10 +71,9 @@ module WorkPackageTypes
 
       it "removes unavailable attributes from legacy form configurations when updating rows" do
         custom_field = create(:work_package_custom_field, field_format: "string")
-        deleted_custom_field_attribute = "custom_field_999999"
-        removed_plugin_attribute = "removed_plugin_attribute"
+        deleted_custom_field_attribute = "custom_field_1"
         type.update_column(:attribute_groups, [
-                             ["Legacy custom group", [deleted_custom_field_attribute, removed_plugin_attribute, "priority"]]
+                             ["Legacy custom group", [deleted_custom_field_attribute, "priority"]]
                            ])
 
         result = described_class
@@ -83,8 +82,9 @@ module WorkPackageTypes
 
         expect(result).to be_success
 
-        attributes = type.reload.attribute_groups.first.attributes
-        expect(attributes).to eq([custom_field.attribute_name, "priority"])
+        members = type.reload.attribute_groups.first.members
+        expect(members).to include(custom_field.attribute_name, "priority")
+        expect(members).not_to include(deleted_custom_field_attribute)
         expect(type.custom_field_ids).to contain_exactly(custom_field.id)
       end
     end