diff --git a/Lib/ruby/rubyrun.swg b/Lib/ruby/rubyrun.swg
index 7c94c4e12..e4c23bde5 100644
--- a/Lib/ruby/rubyrun.swg
+++ b/Lib/ruby/rubyrun.swg
@@ -413,6 +413,7 @@ SWIG_Ruby_SetModule(swig_module_info *pointer)
 {
   /* register a new class */
   VALUE cl = rb_define_class("swig_runtime_data", rb_cObject);
+  rb_undef_alloc_func(cl);
   /* create and store the structure pointer to a global variable */
   swig_runtime_data_type_pointer = Data_Wrap_Struct(cl, 0, 0, pointer);
   rb_define_readonly_variable("$swig_runtime_data_type_pointer" SWIG_RUNTIME_VERSION SWIG_TYPE_TABLE_NAME, &swig_runtime_data_type_pointer);