diff --git a/lib/isccfg/parser.c b/lib/isccfg/parser.c
index d27e6e599a..4ce73dd0b9 100644
--- a/lib/isccfg/parser.c
+++ b/lib/isccfg/parser.c
@@ -1096,7 +1096,7 @@ cfg_print_duration(cfg_printer_t *pctx, const cfg_obj_t *obj) {
 		if (duration.parts[i] > 0) {
 			snprintf(str, durationlen[i] + 2, "%u%c",
 				 (uint32_t)duration.parts[i], indicators[i]);
-			str += durationlen[i] + 1;
+			str += durationlen[i];
 		}
 		if (i == 3 && T) {
 			snprintf(str, 2, "T");