diff --git a/tests/utils/utils_test.c b/tests/utils/utils_test.c
index 211b4d1..223f67d 100644
--- a/tests/utils/utils_test.c
+++ b/tests/utils/utils_test.c
@@ -1014,6 +1014,23 @@
 	printf("(need %d chars, had size=63) %s\n", rc, buf);
 }
 
+void strbuf_test_nolen()
+{
+	char buf[20];
+	struct osmo_strbuf sb = { .buf = buf, .len = sizeof(buf) };
+	uint8_t ubits[] = {0, 0, 0, 1, 0, 1, 1, 1, 0, 0, 1, 0, 1, 0, 1, 0};
+	printf("\n%s\n", __func__);
+
+	OSMO_STRBUF_APPEND_NOLEN(sb, osmo_ubit_dump_buf, ubits, sizeof(ubits));
+	printf("%zu: %s (need=%zu)\n", sb.len, buf, sb.chars_needed);
+	OSMO_STRBUF_APPEND_NOLEN(sb, osmo_ubit_dump_buf, ubits, sizeof(ubits));
+	printf("more: %s (need=%zu)\n", buf, sb.chars_needed);
+
+	sb = (struct osmo_strbuf){ .buf = buf, .len = 10 };
+	OSMO_STRBUF_APPEND_NOLEN(sb, osmo_ubit_dump_buf, ubits, sizeof(ubits));
+	printf("%zu: %s (need=%zu)\n", sb.len, buf, sb.chars_needed);
+}
+
 static void startswith_test_str(const char *str, const char *startswith_str, bool expect_rc)
 {
 	bool rc = osmo_str_startswith(str, startswith_str);
@@ -1059,6 +1076,7 @@
 	osmo_sockaddr_to_str_and_uint_test();
 	osmo_str_tolowupper_test();
 	strbuf_test();
+	strbuf_test_nolen();
 	startswith_test();
 	return 0;
 }
diff --git a/tests/utils/utils_test.ok b/tests/utils/utils_test.ok
index 5783eb1..587c6f0 100644
--- a/tests/utils/utils_test.ok
+++ b/tests/utils/utils_test.ok
@@ -341,6 +341,11 @@
 T minus 10 9 8 7 6 5 4 3 2 1 ... Lift off! -- T minus 10 9 8 7 6 5 4 3 2 1 ... Lift off! -- T minus 10 9 8 7 6 5 4 3 2 1 ... Lift off!
 (need 134 chars, had size=63) T minus 10 9 8 7 6 5 4 3 2 1 ... Lift off! -- T minus 10 9 8 7
 
+strbuf_test_nolen
+20: 0001011100101010 (need=16)
+more: 0001011100101010000 (need=19)
+10: 000101110 (need=9)
+
 startswith_test()
 osmo_str_startswith(NULL, NULL) == true
 osmo_str_startswith("", NULL) == true