diff --git a/debug.c b/debug.c
index 3af7f26275..3dd0f71906 100644
--- a/debug.c
+++ b/debug.c
@@ -499,6 +499,7 @@ pretty_filename(const char *path)
     return path;
 }
 
+#undef ruby_debug_log
 void
 ruby_debug_log(const char *file, int line, const char *func_name, const char *fmt, ...)
 {