diff --git a/src/scrut.c b/src/scrut.c
index 7eccaee..cfdd923 100644
--- a/src/scrut.c
+++ b/src/scrut.c
@@ -17,6 +17,7 @@
  * along with this program. If not, see https://www.gnu.org/licenses/.
  */
 
+#include <assert.h> /* assert(3) */
 #include <stdio.h> /* fprintf(3), stderr, NULL */
 #include <stdlib.h> /* EXIT_FAILURE, EXIT_SUCCESS */
 #include <string.h> /* memset(3), strchr(3) */
@@ -29,6 +30,7 @@
 
 char *program_name = "scrut";
 #define OPTS "bcdefgkprsuwxLS"
+/* this is an array so main:sel's size can be known at compile time */
 static char opts[] = OPTS;
 
 static int
@@ -58,7 +60,10 @@ int main(int argc, char *argv[]) {
 		memset(sel, '\0', sizeof sel);
 		for (int c; (c = getopt(argc, argv, opts)) != -1;) {
 			if ((p = strchr(opts, c)) == NULL) { return usage(argv[0]); }
-			else { sel[p - opts] = c; }
+			else {
+				assert(p - opts < sizeof sel / sizeof *sel); /* bounds check */
+				sel[p - opts] = c;
+			}
 		}
 
 		/* straighten out selections; permute out nulls */
@@ -73,7 +78,7 @@ int main(int argc, char *argv[]) {
 
 	if (optind == argc) { return usage(argv[0]); }
 
-	for (argv += optind ; *argv != NULL; ++argv) {
+	for (argv += optind ; *argv != NULL; argv = &argv[1]) {
 		struct stat buf;
 
 #ifdef __OpenBSD__