diff --git a/lib/acts_as_list/active_record/acts/list.rb b/lib/acts_as_list/active_record/acts/list.rb
index 003150f2..9c29ae6c 100644
--- a/lib/acts_as_list/active_record/acts/list.rb
+++ b/lib/acts_as_list/active_record/acts/list.rb
@@ -112,6 +112,7 @@ def add_new_at
             after_destroy :decrement_positions_on_lower_items
             before_update :check_scope
             after_update :update_positions
+            before_validation :check_top_position
 
             scope :in_list, lambda { where("#{table_name}.#{configuration[:column]} IS NOT NULL") }
           EOV
@@ -441,6 +442,12 @@ def check_scope
           def reload_position
             self.reload
           end
+
+          def check_top_position
+            if send(position_column) && send(position_column) < acts_as_list_top
+              self[position_column] = acts_as_list_top
+            end
+          end
       end
     end
   end
diff --git a/test/shared_zero_based.rb b/test/shared_zero_based.rb
index d684ae63..b448ea89 100644
--- a/test/shared_zero_based.rb
+++ b/test/shared_zero_based.rb
@@ -24,6 +24,11 @@ def test_insert
       assert_equal 0, new.pos
       assert new.first?
       assert new.last?
+
+      new = ZeroBasedMixin.create(parent_id: 1, pos: -500)
+      assert_equal 0, new.pos
+      assert new.first?
+      assert new.last?
     end
 
     def test_reordering