diff --git a/scemu.c b/scemu.c
index bd0f26f..c94a53e 100644
--- a/scemu.c
+++ b/scemu.c
@@ -43,6 +43,8 @@ openprog(char *f, vlong *progsiz)
 	if(fd < 0)
 		return;
 	d = dirfstat(fd);
+	if(d->length > 32768)
+		sysfatal("bad program: bigger than 32K, please shrink it");
 	*progsiz = d->length;
 	free(d);
 	prog = malloc(*progsiz);