diff --git a/kernel/system.h b/kernel/system.h
index 0271e8fab..0cf60fa7d 100644
--- a/kernel/system.h
+++ b/kernel/system.h
@@ -196,5 +196,7 @@ _PROTOTYPE( int do_profbuf, (message *m_ptr) );
 #define do_profbuf do_unused
 #endif
 
+_PROTOTYPE( int do_mapdma, (message *m_ptr) );
+
 #endif	/* SYSTEM_H */