diff --git a/ext/-test-/bug-14834/bug-14384.c b/ext/-test-/bug-14834/bug-14384.c
index 0d4103b5d4..3a16a2d222 100644
--- a/ext/-test-/bug-14834/bug-14384.c
+++ b/ext/-test-/bug-14834/bug-14384.c
@@ -1,6 +1,10 @@
 #include <ruby/ruby.h>
 #include <ruby/debug.h>
 
+#ifndef MAYBE_UNUSED
+# define MAYBE_UNUSED(x) x
+#endif
+
 static NOINLINE(VALUE f(VALUE));
 static NOINLINE(void g(VALUE, void*));
 extern NOINLINE(void Init_bug_14384(void));