X-Git-Url: https://git.distorted.org.uk/~mdw/catacomb/blobdiff_plain/0f00dc4c8eb47e67bc0f148c2dd109f73a451e0a..8f2287ef5c05d496fcb9b012629af007fe56f897:/progs/factorial.c

diff --git a/progs/factorial.c b/progs/factorial.c
index a46debd1..975c698c 100644
--- a/progs/factorial.c
+++ b/progs/factorial.c
@@ -135,7 +135,7 @@ int main(int argc, char *argv[])
   xx = mp_readstring(MP_NEW, argv[optind], &p, 0);
   while (isspace((unsigned char)*p))
     p++;
-  if (!xx || *p || MP_CMP(xx, >, ulmax))
+  if (!xx || *p || MP_CMP(xx, <, MP_ZERO) || MP_CMP(xx, >, ulmax))
     die(EXIT_FAILURE, "bad integer `%s'", argv[optind]);
   x = mp_toulong(xx);
   mp_drop(xx);