diff --git a/app/controllers/ajax/list_controller.rb b/app/controllers/ajax/list_controller.rb
index e934f497..c952cb59 100644
--- a/app/controllers/ajax/list_controller.rb
+++ b/app/controllers/ajax/list_controller.rb
@@ -95,6 +95,9 @@ class Ajax::ListController < AjaxController
 
     target_user = User.find_by_screen_name!(params[:user])
 
+    raise Errors::ListingSelfBlockedOther if current_user.blocking?(target_user)
+    raise Errors::ListingOtherBlockedSelf if target_user.blocking?(current_user)
+
     if add
       list.add_member target_user if list.members.find_by_user_id(target_user.id).nil?
       @response[:checked] = true
diff --git a/lib/errors.rb b/lib/errors.rb
index b577491e..10cb15cd 100644
--- a/lib/errors.rb
+++ b/lib/errors.rb
@@ -85,5 +85,11 @@ module Errors
 
   class ReactingOtherBlockedSelf < OtherBlockedSelf
   end
+
+  class ListingSelfBlockedOther < SelfBlockedOther
+  end
+
+  class ListingOtherBlockedSelf < OtherBlockedSelf
+  end
   # endregion
 end