1 files changed, 4 insertions, 0 deletions
diff --git a/apps/x509.c b/apps/x509.c
index 05aa5547cd..9e5101259f 100644
--- a/apps/x509.c
+++ b/apps/x509.c
@@ -261,6 +261,10 @@ int x509_main(int argc, char **argv)
             CAserial = opt_arg();
             break;
         case OPT_SET_SERIAL:
+            if (sno != NULL) {
+                /* Cannot be supplied twice */
+                goto opthelp;
+            }
             if ((sno = s2i_ASN1_INTEGER(NULL, opt_arg())) == NULL)
                 goto opthelp;
             break;