diff --git a/ext/-test-/fatal/extconf.rb b/ext/-test-/fatal/extconf.rb
index d5849c0733..ca51178a18 100644
--- a/ext/-test-/fatal/extconf.rb
+++ b/ext/-test-/fatal/extconf.rb
@@ -1,2 +1,3 @@
 # frozen_string_literal: false
-create_makefile("-test-/fatal/rb_fatal")
+require_relative "../auto_ext.rb"
+auto_ext
diff --git a/ext/-test-/fatal/init.c b/ext/-test-/fatal/init.c
new file mode 100644
index 0000000000..3b71708789
--- /dev/null
+++ b/ext/-test-/fatal/init.c
@@ -0,0 +1,10 @@
+#include "ruby.h"
+
+#define init(n) {void Init_##n(VALUE klass); Init_##n(klass);}
+
+void
+Init_fatal(void)
+{
+    VALUE klass = rb_define_module("Bug");
+    TEST_INIT_FUNCS(init);
+}
diff --git a/ext/-test-/fatal/rb_fatal.c b/ext/-test-/fatal/rb_fatal.c
index eedbc51f8b..6c7bb89628 100644
--- a/ext/-test-/fatal/rb_fatal.c
+++ b/ext/-test-/fatal/rb_fatal.c
@@ -13,8 +13,7 @@ ruby_fatal(VALUE obj, VALUE msg)
 }
 
 void
-Init_rb_fatal(void)
+Init_rb_fatal(VALUE mBug)
 {
-    VALUE mBug = rb_define_module("Bug");
     rb_define_singleton_method(mBug, "rb_fatal", ruby_fatal, 1);
 }
diff --git a/test/ruby/test_fiber.rb b/test/ruby/test_fiber.rb
index 1fb6103d8a..45e5d12092 100644
--- a/test/ruby/test_fiber.rb
+++ b/test/ruby/test_fiber.rb
@@ -424,7 +424,7 @@ class TestFiber < Test::Unit::TestCase
   end
 
   def test_fatal_in_fiber
-    assert_in_out_err(["-r-test-/fatal/rb_fatal", "-e", <<-EOS], "", [], /ok/)
+    assert_in_out_err(["-r-test-/fatal", "-e", <<-EOS], "", [], /ok/)
       Fiber.new{
         Bug.rb_fatal "ok"
       }.resume