diff --git a/app/models/heart.rb b/app/models/heart.rb
index c811f80..f598d1c 100644
--- a/app/models/heart.rb
+++ b/app/models/heart.rb
@@ -24,9 +24,11 @@ class Heart < (defined?(ApplicationRecord) == 'constant' ? ApplicationRecord : A
   belongs_to :heartable, :polymorphic => true
   belongs_to :user
 
+  attribute :skip_validate_user, :boolean
+
   validates_presence_of :user
   validates_uniqueness_of :user_id, :scope => [:heartable_type, :heartable_id]
-  validate :validate_user
+  validate :validate_user, :unless => :skip_validate_user
 
   def self.of_projects(*args)
     projects = args.size > 0 ? args.shift : Project.none
diff --git a/lib/tasks/redmine_hearts.rake b/lib/tasks/redmine_hearts.rake
index 891fbf5..7d16227 100644
--- a/lib/tasks/redmine_hearts.rake
+++ b/lib/tasks/redmine_hearts.rake
@@ -88,7 +88,7 @@ namespace :redmine_hearts do
 
     num_of_heart_before_processing = Heart.count
 
-    VoteOnIssue.where('vote_val > 0').each do |vote|
+    VoteOnIssue.where('vote_val > 0').where.not(issue: nil, user: nil).each do |vote|
       issue = vote.issue
       user = vote.user
       datetime = vote.created_at || Time.now
@@ -100,6 +100,7 @@ namespace :redmine_hearts do
           :user => user,
           :created_at => datetime,
           :updated_at => datetime,
+          :skip_validate_user => true,
         )
       end
     end