--- libprelude-5.1.1/bindings/ruby/Prelude.cxx.ruby27	2019-10-15 05:33:03.117000000 +0900
+++ libprelude-5.1.1/bindings/ruby/Prelude.cxx	2020-01-19 20:13:37.324557838 +0900
@@ -1260,7 +1260,7 @@ SWIGRUNTIME void SWIG_RubyInitializeTrac
     swig_ruby_trackings = (st_table*)NUM2SWIG(trackings_value);
   }
 
-  rb_define_virtual_variable("SWIG_TRACKINGS_COUNT", swig_ruby_trackings_count, NULL);
+  rb_define_virtual_variable("SWIG_TRACKINGS_COUNT", swig_ruby_trackings_count, (rb_gvar_setter_t *)NULL);
 }
 
 /* Add a Tracking from a C/C++ struct to a Ruby object */