diff --git a/sbotc.c b/sbotc.c
index 1284ef6..f2a60cc 100644
--- a/sbotc.c
+++ b/sbotc.c
@@ -633,7 +633,7 @@ static int bs_read_error(struct boxs *bs, int errfd, enum pkt_flags flags, size_
 	if (flags & pkt_flags_json && len == 4) {
 		char buf[4];
 		if (bs_read(bs, buf, 4) < 0) return -1;
-		if (strncmp(buf, "true", 0) == 0) {
+		if (strncmp(buf, "true", 4) == 0) {
 			return 0;
 		}
 		if (write_all(errfd, buf, 4) < 0) return -1;