diff --git a/lib/tasks/2017_07_18_clean_followed_dossiers.rake b/lib/tasks/2017_07_18_clean_followed_dossiers.rake
new file mode 100644
index 000000000..89058da02
--- /dev/null
+++ b/lib/tasks/2017_07_18_clean_followed_dossiers.rake
@@ -0,0 +1,15 @@
+namespace :'2017_07_18_clean_followed_dossiers' do
+  task clean: :environment do
+    Follow.where(gestionnaire_id: nil).destroy_all
+    Follow.where(dossier_id: nil).destroy_all
+
+    duplicate_follows = Follow.group('gestionnaire_id', 'dossier_id').count.select{ |_gestionnaire_id_dossier_id, count| count > 1 }.keys
+
+    duplicate_ids = duplicate_follows.map { |gestionnaire_id, dossier_id| Follow.where(gestionnaire_id: gestionnaire_id, dossier_id: dossier_id).pluck(:id) }
+
+    duplicate_ids.each do |ids|
+      ids.pop
+      Follow.where(id: ids).destroy_all
+    end
+  end
+end