I tried to fix it int load.c, but failed rubyspec:
http://80x24.org/spew/m/1436044472-18990-1-git-send-email-e / 80x24.org.txt

However, this one-liner seems to work:
~~~
--- a/enumerator.c
+++ b/enumerator.c
@@ -2060,6 +2060,7 @@ InitVM_Enumerator(void)
     rb_define_method(rb_cYielder, "yield", yielder_yield, -2);
     rb_define_method(rb_cYielder, "<<", yielder_yield_push, -2);
 
+    rb_provide("enumerator.rb");
     rb_provide("enumerator.so");	/* for backward compatibility */
 }
 
~~~

I'm not sure if we need something similar for complex and rational,
not sure if they were really used via require in the past...

http://80x24.org/spew/m/1436044803-31588-1-git-send-email-e / 80x24.org.txt