--- ./test/fiddle/helper.rb.origin	2023-06-26 03:52:39.462501191 +0000
+++ ./test/fiddle/helper.rb	2023-06-26 03:54:44.778120617 +0000
@@ -101,6 +101,12 @@
     mobjs=%w!floats.o sin.o!
     funcs=%w!sin sinf strcpy strncpy!
     expfile='dltest.exp'
+    case [0].pack('L!').size
+    when 8
+      # 64-bit ruby
+      cobjs=%w!strcpy_64.o!
+      mobjs=%w!floats_64.o sin_64.o!
+    end
     require 'tmpdir'
     Dir.mktmpdir do |_dir|
       begin