diff --git a/include/sys/cdefs.h b/include/sys/cdefs.h
index f7c6a11..92eb783 100644
--- a/include/sys/cdefs.h
+++ b/include/sys/cdefs.h
@@ -26,3 +26,7 @@
 #ifndef __RCSID
 #define __RCSID(x)
 #endif
+
+#ifndef __COPYRIGHT
+#define __COPYRIGHT(x)
+#endif