diff --git a/app/controllers/body_trackers_controller.rb b/app/controllers/body_trackers_controller.rb
index 6cd622b..2c45243 100644
--- a/app/controllers/body_trackers_controller.rb
+++ b/app/controllers/body_trackers_controller.rb
@@ -9,6 +9,8 @@ class BodyTrackersController < ApplicationController
   end
 
   def defaults
+    failed_objects = []
+
     # Units
     available_units = @project.units.pluck(:shortname, :id).to_h
     defaults = Unit.where(project: nil).map do |u|
@@ -38,7 +40,11 @@ class BodyTrackersController < ApplicationController
           attrs['formula_attributes']['unit_id'] = available_units[q.formula.unit.shortname]
         end
         obj = @project.quantities.create(attrs)
-        available_quantities[[q.name, q.domain]] = obj if obj.persisted?
+        if obj.persisted?
+          available_quantities[[q.name, q.domain]] = obj
+        else
+          failed_objects << obj
+        end
       end
     end
 
@@ -62,6 +68,13 @@ class BodyTrackersController < ApplicationController
     flash[:notice] += " and #{new_sources.length > 0 ? new_sources.length : "no" } new" \
       " #{'source'.pluralize(new_sources.length)}"
 
+    if failed_objects.present?
+      flash[:notice] += " (loading #{failed_objects.length} objects failed, see errors)"
+      flash[:error] = failed_objects.map do |o|
+        "<p>#{o.class.name} #{o.name}: #{o.errors.full_messages.join(', ')}</p>"
+      end.join.html_safe
+    end
+
     redirect_to :back
   end
 end
diff --git a/app/models/quantity.rb b/app/models/quantity.rb
index 1224801..11840d7 100644
--- a/app/models/quantity.rb
+++ b/app/models/quantity.rb
@@ -44,6 +44,7 @@ class Quantity < ActiveRecord::Base
     end
   end
 
+  # TODO: move as an association extension module
   def self.filter(project, filters)
     quantities = all
 
diff --git a/config/locales/en.yml b/config/locales/en.yml
index 8e0f630..fa29439 100644
--- a/config/locales/en.yml
+++ b/config/locales/en.yml
@@ -47,11 +47,11 @@ en:
         formula:
           attributes:
             code:
-              disallowed_syntax: 'cannot be parsed: %{syntax}'
-              disallowed_token: 'includes disallowed token: "%{token}"'
-              disallowed_keyword: 'includes disallowed keyword: "%{keyword}"'
-              disallowed_method: 'includes disallowed method call: "%{method}"'
-              unknown_dependency: 'contains undefined dependency: %{identifier}'
+              disallowed_syntax: 'cannot be parsed "%{syntax}"'
+              disallowed_token: 'includes disallowed token "%{token}"'
+              disallowed_keyword: 'includes disallowed keyword "%{keyword}"'
+              disallowed_method: 'includes disallowed method call "%{method}"'
+              unknown_dependency: 'contains undefined dependency "%{identifier}"'
               computation_failed: 'computation failed for "%{quantity}": %{description}
                 (%{count} values missing)'
   body_trackers: