Index: lib/mruby/build.rb
--- lib/mruby/build.rb.orig
+++ lib/mruby/build.rb
@@ -443,7 +443,7 @@ EOS
       targets << filename(".") if File.directory? "./bintest"
       mrbc = @gems["mruby-bin-mrbc"] ? exefile("#{@build_dir}/bin/mrbc") : mrbcfile
       env = {"BUILD_DIR" => @build_dir, "MRBCFILE" => mrbc}
-      sh env, "ruby test/bintest.rb#{verbose_flag} #{targets.join ' '}"
+      sh env, "${RUBY} test/bintest.rb#{verbose_flag} #{targets.join ' '}"
     end
 
     def print_build_summary