diff -r d417adf19a53 sys/src/cmd/8c/cgen.c
--- a/sys/src/cmd/8c/cgen.c	Thu May 24 13:41:08 2018 +0100
+++ b/sys/src/cmd/8c/cgen.c	Thu May 24 12:09:05 2018 -0400
@@ -994,7 +994,8 @@
 
 	case OCAST:
 		if(nn == Z) {
-			nullwarn(l, Z);
+			if(n->type != types[TVOID])
+				nullwarn(l, Z);
 			break;
 		}
 		/*