diff --git a/app/controllers/body_trackers_controller.rb b/app/controllers/body_trackers_controller.rb
index 2c45243..7441f65 100644
--- a/app/controllers/body_trackers_controller.rb
+++ b/app/controllers/body_trackers_controller.rb
@@ -32,23 +32,21 @@ class BodyTrackersController < ApplicationController
         attrs = q.attributes.except('id', 'project_id', 'parent_id', 'lft', 'rgt',
                                     'created_at', 'updated_at')
         if q.parent
-          attrs['parent_id'] = available_quantities[[q.parent.name, q.parent.domain]].id
+          attrs['parent'] = available_quantities[[q.parent.name, q.parent.domain]]
         end
         if q.formula
           attrs['formula_attributes'] = q.formula.attributes
             .except('id', 'quantity_id', 'unit_id', 'created_at', 'updated_at')
           attrs['formula_attributes']['unit_id'] = available_units[q.formula.unit.shortname]
         end
-        obj = @project.quantities.create(attrs)
-        if obj.persisted?
-          available_quantities[[q.name, q.domain]] = obj
-        else
-          failed_objects << obj
-        end
+        available_quantities[[q.name, q.domain]] = @project.quantities.build(attrs)
       end
     end
+    Quantity.transaction do
+      failed_objects += available_quantities.values.reject { |o| o.persisted? || o.save }
+    end
 
-    new_quantities_count = available_quantities.length - quantities_count
+    new_quantities_count = @project.quantities(true).size - quantities_count
     flash[:notice] += ", #{new_quantities_count > 0 ? new_quantities_count : "no" } new" \
       " #{'quantity'.pluralize(new_quantities_count)}"
 
diff --git a/app/models/formula.rb b/app/models/formula.rb
index 01d9a75..659cecc 100644
--- a/app/models/formula.rb
+++ b/app/models/formula.rb
@@ -58,7 +58,15 @@ class Formula < ActiveRecord::Base
     identifiers, parts = parser.parse
     errors = parser.errors
 
-    quantities = Quantity.where(project: self.quantity.project, name: identifiers.to_a)
+    project = self.quantity.project
+    quantities =
+      if project
+        # This is required to properly validate with in-memory records, e.g.
+        # during import of defaults
+        project.quantities.select { |q| identifiers.include?(q.name) }
+      else
+        Quantity.where(project: nil, name: identifiers.to_a)
+      end
     identifiers -= quantities.map(&:name)
     models = identifiers.map(&:safe_constantize).compact || []
     (identifiers - models.map(&:class_name)).each do |i|
diff --git a/lib/body_tracking/project_patch.rb b/lib/body_tracking/project_patch.rb
index 28152ec..44899f4 100644
--- a/lib/body_tracking/project_patch.rb
+++ b/lib/body_tracking/project_patch.rb
@@ -1,7 +1,7 @@
 module BodyTracking::ProjectPatch
   Project.class_eval do
     has_many :sources, dependent: :destroy
-    has_many :quantities, -> { order "lft" }, dependent: :destroy
+    has_many :quantities, -> { order "lft" }, inverse_of: :project, dependent: :destroy
     has_many :units, dependent: :destroy
 
     has_many :foods, -> { order "foods.name" }, dependent: :destroy,