diff --git a/test/dl/test_cfunc.rb b/test/dl/test_cfunc.rb
index 209c8f3731..e18a096611 100644
--- a/test/dl/test_cfunc.rb
+++ b/test/dl/test_cfunc.rb
@@ -65,10 +65,12 @@ module DL
     end
 
     def test_last_error
-      f = Function.new(@cf, [TYPE_VOIDP, TYPE_VOIDP])
-      assert_nil CFunc.last_error
-      str = f.call("000", "123")
-      assert_not_nil CFunc.last_error
+      Thread.new do
+        f = Function.new(@cf, [TYPE_VOIDP, TYPE_VOIDP])
+        assert_nil CFunc.last_error
+        str = f.call("000", "123")
+        assert_not_nil CFunc.last_error
+      end.join
     end
   end
 end