diff --git a/test/core/test_ulid_class.rb b/test/core/test_ulid_class.rb
index ce4ea10..d382816 100644
--- a/test/core/test_ulid_class.rb
+++ b/test/core/test_ulid_class.rb
@@ -221,7 +221,8 @@ def test_new
     err = assert_raises(NoMethodError) do
       ULID.new(milliseconds: 0, entropy: 42)
     end
-    assert_match(/private method `new' called/, err.message)
+    # NoMethodError#private_call? will not fit. Checking the error message is not a good test, but required at here
+    assert_match(/private method (`|')new' called/, err.message)
   end
 
   def test_normalize