diff --git a/sys/src/9/ip/nullmedium.c b/sys/src/9/ip/nullmedium.c
index bc575c05c..21cb44354 100644
--- a/sys/src/9/ip/nullmedium.c
+++ b/sys/src/9/ip/nullmedium.c
@@ -19,8 +19,9 @@ nullunbind(Ipifc*)
 }
 
 static void
-nullbwrite(Ipifc*, Block*, int, uchar*)
+nullbwrite(Ipifc*, Block *bp, int, uchar*)
 {
+	freeb(bp);
 	error("nullbwrite");
 }