diff --git a/app/controllers/contexts_controller.rb b/app/controllers/contexts_controller.rb
index b1ff4c1b..c6510c40 100644
--- a/app/controllers/contexts_controller.rb
+++ b/app/controllers/contexts_controller.rb
@@ -83,7 +83,7 @@ class ContextsController < ApplicationController
       end
       format.xml do
         if @context.new_record?
-          render_failure @context.errors.to_xml.html_safe, 409
+          render_failure @context.errors.full_messages.to_xml(root: "errors", skip_types: true).html_safe, 409
         else
           head :created, :location => context_url(@context)
         end
diff --git a/app/controllers/projects_controller.rb b/app/controllers/projects_controller.rb
index e116bb08..5d75d7c9 100644
--- a/app/controllers/projects_controller.rb
+++ b/app/controllers/projects_controller.rb
@@ -186,7 +186,7 @@ class ProjectsController < ApplicationController
       end
       format.xml do
         if @project.new_record?
-          render_failure @project.errors.to_xml.html_safe, 409
+          render_failure @project.errors.full_messages.to_xml(root: "errors", skip_types: true).html_safe, 409
         else
           head :created, :location => project_url(@project), :text => @project.id
         end
diff --git a/app/controllers/todos_controller.rb b/app/controllers/todos_controller.rb
index 9c98c88d..1c852420 100644
--- a/app/controllers/todos_controller.rb
+++ b/app/controllers/todos_controller.rb
@@ -154,7 +154,7 @@ class TodosController < ApplicationController
           if @saved
             head :created, :location => todo_url(@todo)
           else
-            render_failure @todo.errors.to_xml.html_safe, 409
+            render_failure @todo.errors.full_messages.to_xml(root: "errors", skip_types: true).html_safe, 409
           end
         end
       end
@@ -438,7 +438,7 @@ class TodosController < ApplicationController
     rescue ActiveRecord::RecordInvalid => exception
       record = exception.record
       if record.is_a?(Dependency)
-        record.errors.each { |key, value| @todo.errors[key] << value }
+        record.errors.each { |key, value| @todo.errors.add(key, value) }
       end
       @saved = false
     end
@@ -1192,7 +1192,7 @@ end
     begin
       parse_date_per_user_prefs(date)
     rescue
-      @todo.errors[:base] << error_msg
+      @todo.errors.add(:base, error_msg)
     end
   end
 
diff --git a/app/controllers/users_controller.rb b/app/controllers/users_controller.rb
index 8198025a..30b63172 100644
--- a/app/controllers/users_controller.rb
+++ b/app/controllers/users_controller.rb
@@ -125,7 +125,7 @@ class UsersController < ApplicationController
         unless user.new_record?
           render :body => t('users.user_created'), :status => 200
         else
-          render_failure user.errors.to_xml, 409
+          render_failure user.errors.full_messages.to_xml(root: "errors", skip_types: true), 409
         end
         return
       end
diff --git a/app/models/recurring_todos/abstract_recurrence_pattern.rb b/app/models/recurring_todos/abstract_recurrence_pattern.rb
index 91276f2e..2ad33b34 100644
--- a/app/models/recurring_todos/abstract_recurrence_pattern.rb
+++ b/app/models/recurring_todos/abstract_recurrence_pattern.rb
@@ -80,11 +80,11 @@ module RecurringTodos
     end
 
     def validate_not_blank(object, msg)
-      errors[:base] << msg if object.blank?
+      errors.add(:base, msg) if object.blank?
     end
 
     def validate_not_nil(object, msg)
-      errors[:base] << msg if object.nil?
+      errors.add(:base, msg) if object.nil?
     end
 
     def validate
@@ -100,7 +100,7 @@ module RecurringTodos
       when "ends_on_end_date"
         validate_not_blank(end_date, "The end date needs to be filled in for 'Ends on'")
       else
-        errors[:base] << "The end of the recurrence is not selected" unless ends_on == "no_end_date"
+        errors.add(:base, "The end of the recurrence is not selected") unless ends_on == "no_end_date"
       end
     end
 
@@ -113,7 +113,7 @@ module RecurringTodos
         validate_not_nil(show_always?, "Please select when to show the action")
         validate_not_blank(show_from_delta, "Please fill in the number of days to show the todo before the due date") unless show_always?
       else
-        errors[:base] << "Unexpected value of recurrence target selector '#{target}'"
+        errors.add(:base, "Unexpected value of recurrence target selector '#{target}'")
       end
     end
 
diff --git a/app/models/recurring_todos/daily_recurrence_pattern.rb b/app/models/recurring_todos/daily_recurrence_pattern.rb
index 35a0ea16..8caaa716 100644
--- a/app/models/recurring_todos/daily_recurrence_pattern.rb
+++ b/app/models/recurring_todos/daily_recurrence_pattern.rb
@@ -24,7 +24,7 @@ module RecurringTodos
 
     def validate
       super
-      errors[:base] << "Every other nth day may not be empty for this daily recurrence setting" if (!only_work_days?) && every_x_days.blank?
+      errors.add(:base, "Every other nth day may not be empty for this daily recurrence setting") if (!only_work_days?) && every_x_days.blank?
     end
 
     def get_next_date(previous)
diff --git a/app/models/recurring_todos/weekly_recurrence_pattern.rb b/app/models/recurring_todos/weekly_recurrence_pattern.rb
index 5ba3a13f..c554b016 100644
--- a/app/models/recurring_todos/weekly_recurrence_pattern.rb
+++ b/app/models/recurring_todos/weekly_recurrence_pattern.rb
@@ -30,7 +30,7 @@ module RecurringTodos
       super
       validate_not_blank(every_x_week, "Every other nth week may not be empty for weekly recurrence setting")
       something_set = %w{ sunday monday tuesday wednesday thursday friday saturday }.inject(false) { |set, day| set || send("on_#{day}") }
-      errors[:base] << "You must specify at least one day on which the todo recurs" unless something_set
+      errors.add(:base, "You must specify at least one day on which the todo recurs") unless something_set
     end
 
     def get_next_date(previous)
diff --git a/db/migrate/038_projects_contexts_remove_not_null_from_position.rb b/db/migrate/038_projects_contexts_remove_not_null_from_position.rb
index af167857..45ea7c26 100644
--- a/db/migrate/038_projects_contexts_remove_not_null_from_position.rb
+++ b/db/migrate/038_projects_contexts_remove_not_null_from_position.rb
@@ -1,7 +1,7 @@
 class ProjectsContextsRemoveNotNullFromPosition < ActiveRecord::Migration[5.2]
   def self.up
-    change_column :projects, :position, :integer, {:null => true, :default => nil}
-    change_column :contexts, :position, :integer, {:null => true, :default => nil}
+    change_column :projects, :position, :integer, :null => true, :default => nil
+    change_column :contexts, :position, :integer, :null => true, :default => nil
   end
 
   def self.down
@@ -10,13 +10,13 @@ class ProjectsContextsRemoveNotNullFromPosition < ActiveRecord::Migration[5.2]
       project.position = 0 if !project.position?
       project.save
     end
-    change_column :projects, :position, :integer, {:null => false, :default => nil}
+    change_column :projects, :position, :integer, :null => false, :default => nil
 
     @contexts = Context.find(:all)
     @contexts.each do |context|
       context.position = 0 if !context.position?
       context.save
     end
-    change_column :contexts, :position, :integer, {:null => false, :default => nil}
+    change_column :contexts, :position, :integer, :null => false, :default => nil
   end
 end
diff --git a/test/models/todo_test.rb b/test/models/todo_test.rb
index c257c0fe..dd1e084b 100644
--- a/test/models/todo_test.rb
+++ b/test/models/todo_test.rb
@@ -102,7 +102,7 @@ class TodoTest < ActiveSupport::TestCase
     @not_completed2
     assert_equal :active, @not_completed2.aasm.current_state
     @not_completed2.show_from = Time.zone.now + 1.week
-    assert @not_completed2.save, "should have saved successfully" + @not_completed2.errors.to_xml
+    assert @not_completed2.save, "should have saved successfully " + @not_completed2.errors.full_messages.to_s
     assert_equal :deferred, @not_completed2.aasm.current_state
   end
 
@@ -112,14 +112,14 @@ class TodoTest < ActiveSupport::TestCase
     todo.show_from = next_week
     todo.context_id = 1
     todo.description = 'foo'
-    assert todo.save, "should have saved successfully" + todo.errors.to_xml
+    assert todo.save, "should have saved successfully" + todo.errors.full_messages.to_s
     assert_equal :deferred, todo.aasm.current_state
   end
 
   def test_create_a_new_deferred_todo_by_passing_attributes
     user = users(:other_user)
     todo = user.todos.build(:show_from => next_week, :context_id => 1, :description => 'foo')
-    assert todo.save, "should have saved successfully" + todo.errors.to_xml
+    assert todo.save, "should have saved successfully " + todo.errors.full_messages.to_s
     assert_equal :deferred, todo.aasm.current_state
   end
 
@@ -551,7 +551,7 @@ class TodoTest < ActiveSupport::TestCase
     new_path = attachment.file.path
 
     # then the attachment should be there
-    assert File.exists?(new_path), "attachment should be on file system"
+    assert File.exist?(new_path), "attachment should be on file system"
     assert_equal 1, todo.attachments.reload.count, "should have one attachment"
 
     # When I destroy the todo
@@ -559,7 +559,7 @@ class TodoTest < ActiveSupport::TestCase
 
     # Then the attachement and file should nogt be there anymore
     assert_equal 0, todo.user.attachments.reload.count
-    assert !File.exists?(new_path), "attachment should not be on file system"
+    assert !File.exist?(new_path), "attachment should not be on file system"
   end
 
   def test_destroying_action_activates_successors