Index: lib/better_nested_set.rb
===================================================================
--- lib/better_nested_set.rb	(revision 75)
+++ lib/better_nested_set.rb	(working copy)
@@ -471,6 +471,19 @@
               new_parent = target[parent_col_name].nil? ? 'NULL' : target[parent_col_name]
             end
             
+            update_condition = "(#{scope_condition})" <<
+              " AND (" <<
+                "(#{left_col_name} BETWEEN #{a} AND #{b})" <<
+                " OR " <<
+                "(#{left_col_name} BETWEEN #{c} AND #{d})" <<
+                " OR " <<
+                "(#{right_col_name} BETWEEN #{a} AND #{b})" <<
+                " OR " <<
+                "(#{right_col_name} BETWEEN #{c} AND #{d})" <<
+                " OR " <<
+                "(#{self.class.primary_key} = #{self.id})" <<
+              ")"
+            
             base_set_class.update_all("\
               #{left_col_name} = CASE \
                 WHEN #{left_col_name} BETWEEN #{a} AND #{b} THEN #{left_col_name} + #{d - b} \
@@ -483,7 +496,7 @@
               #{parent_col_name} = CASE \
                 WHEN #{self.class.primary_key} = #{self.id} THEN #{new_parent} \
                 ELSE #{parent_col_name} END",
-              scope_condition)
+              update_condition)
             self.reload
             target.reload
           end