diff --git a/lib/ostruct.rb b/lib/ostruct.rb
index a8763da..bc18028 100644
--- a/lib/ostruct.rb
+++ b/lib/ostruct.rb
@@ -155,10 +155,18 @@ def initialize(hash=nil)
   end
 
   private def update_to_values!(hash) # :nodoc:
+    old_table = @table
     @table = {}
     hash.each_pair do |k, v|
       set_ostruct_member_value!(k, v)
     end
+    old_table&.each_key do |key|
+      next if @table.key?(key)
+      begin
+        singleton_class!.remove_method(key, "#{key}=")
+      rescue NameError
+      end
+    end
   end
 
   #