diff --git a/lib/idmapping.c b/lib/idmapping.c
index 248269c8..a46c8c24 100644
--- a/lib/idmapping.c
+++ b/lib/idmapping.c
@@ -52,23 +52,19 @@ get_map_ranges(int ranges, int argc, char **argv)
 	/* Gather up the ranges from the command line */
 	m = mappings;
 	for (int i = 0; i < ranges * 3; i+=3, m++) {
-		if (a2ul(&m->upper, argv[i + 0], NULL, 0, 0, UINT_MAX) == -1) {
+		if (a2ul(&m->upper, argv[i + 0], NULL, 0, 0, UINT_MAX - 1) == -1) {
 			if (errno == ERANGE)
 				fprintf(log_get_logfd(), _( "%s: subuid overflow detected.\n"), log_get_progname());
 			free(mappings);
 			return NULL;
 		}
-		if (a2ul(&m->lower, argv[i + 1], NULL, 0, 0, UINT_MAX) == -1) {
+		if (a2ul(&m->lower, argv[i + 1], NULL, 0, 0, UINT_MAX - 1) == -1) {
 			if (errno == ERANGE)
 				fprintf(log_get_logfd(), _( "%s: subuid overflow detected.\n"), log_get_progname());
 			free(mappings);
 			return NULL;
 		}
-		if (a2ul(&m->count, argv[i + 2], NULL, 0, 0,
-		         MIN(MIN(UINT_MAX, ULONG_MAX - 1) - m->lower,
-		             MIN(UINT_MAX, ULONG_MAX - 1) - m->upper))
-		    == -1)
-		{
+		if (a2ul(&m->count, argv[i + 2], NULL, 0, 1, UINT_MAX - MAX(m->lower, m->upper)) == -1) {
 			if (errno == ERANGE)
 				fprintf(log_get_logfd(), _( "%s: subuid overflow detected.\n"), log_get_progname());
 			free(mappings);