diff --git a/app/models/organization.rb b/app/models/organization.rb
index d718866..c540154 100644
--- a/app/models/organization.rb
+++ b/app/models/organization.rb
@@ -28,7 +28,7 @@ class Organization < Profile
   end
 
   def find_pending_validation(code)
-    validations.pending.find { |pending| pending.code == code }
+    validations.pending.find(:first, :conditions => {:code => code})
   end
 
   def processed_validations
@@ -36,7 +36,7 @@ class Organization < Profile
   end
 
   def find_processed_validation(code)
-    validations.finished.find { |pending| pending.code == code }
+    validations.finished.find(:first, :conditions => {:code => code})
   end
 
   def is_validation_entity?
@@ -93,4 +93,7 @@ class Organization < Profile
     [contact_email.blank? ? nil : contact_email].compact + admins.map(&:email)
   end
 
+  def already_request_membership?(person)
+    self.tasks.pending.find_by_requestor_id(person.id, :conditions => { :type => 'AddMember' })
+  end
 end
diff --git a/app/models/profile.rb b/app/models/profile.rb
index e9498d2..883b735 100644
--- a/app/models/profile.rb
+++ b/app/models/profile.rb
@@ -475,7 +475,7 @@ private :generate_url, :url_options
   def add_member(person)
     if self.has_members?
       if self.closed?
-        AddMember.create!(:person => person, :organization => self)
+        AddMember.create!(:person => person, :organization => self) unless self.already_request_membership?(person)
       else
         self.affiliate(person, Profile::Roles.member(environment.id))
       end
diff --git a/app/models/task.rb b/app/models/task.rb
index 5f5f82e..d7b8f04 100644
--- a/app/models/task.rb
+++ b/app/models/task.rb
@@ -176,15 +176,10 @@ class Task < ActiveRecord::Base
     end
   end
 
-  class << self
+  named_scope :pending, :conditions => { :status =>  Task::Status::ACTIVE }
+  named_scope :finished, :conditions => { :status =>  [Task::Status::CANCELLED, Task::Status::FINISHED] }
 
-    def pending
-      self.find(:all, :conditions => { :status =>  Task::Status::ACTIVE })
-    end
-    
-    def finished
-      self.find(:all, :conditions => { :status =>  [Task::Status::CANCELLED, Task::Status::FINISHED]})
-    end
+  class << self
 
     # generates a random code string consisting of length characters (or 36 by
     # default) in the ranges a-z and 0-9
diff --git a/test/unit/community_test.rb b/test/unit/community_test.rb
index c9bfd52..450829f 100644
--- a/test/unit/community_test.rb
+++ b/test/unit/community_test.rb
@@ -187,4 +187,17 @@ class CommunityTest < Test::Unit::TestCase
       Community.create_after_moderation(person, {:environment => env, :name => 'Example'})
     end
   end
+
+  should 'not create new request membership if it already exists' do
+    community = fast_create(Community)
+    community.closed = true
+    community.save
+    assert_difference AddMember, :count do
+      community.add_member(person)
+    end
+
+    assert_no_difference AddMember, :count do
+      community.add_member(person)
+    end
+  end
 end
--
libgit2 0.21.2