diff --git a/image-sixel.c b/image-sixel.c
index f6eaade3..c37e2cce 100644
--- a/image-sixel.c
+++ b/image-sixel.c
@@ -487,9 +487,9 @@ static void
 sixel_print_add(char **buf, size_t *len, size_t *used, const char *s,
     size_t slen)
 {
-	if (*used + slen >= *len + 1) {
+	while (*used + slen >= *len + 1) {
+		*buf = xreallocarray(*buf, 2, *len);
 		(*len) *= 2;
-		*buf = xrealloc(*buf, *len);
 	}
 	memcpy(*buf + *used, s, slen);
 	(*used) += slen;