--- a/native/tests/tests.cpp
+++ b/native/tests/tests.cpp
@@ -16,7 +16,7 @@
   Window off(0);
   CHECK(disabled(off));
   CHECK(normalize("MiXed") == "mixed");
-  CHECK(first_or_null("") == NULL);
+  CHECK(first_or_null("") == nullptr);
   CHECK(std::strcmp(first_or_null("a"), "a") == 0);
   std::cout << (failures ? "FAILED" : "PASSED") << "\n";
   return failures ? 1 : 0;