diff --git a/test/lib/str.c b/test/lib/str.c
index 3cc9dfe..e620453 100644
--- a/test/lib/str.c
+++ b/test/lib/str.c
@@ -18,6 +18,8 @@
 static const char str5[] = "0x9876543210the last time I was deloused";
 static const char str6[] = "0778octal is seldom used";
 static const char str7[] = "707it is a piece of computing history";
+static const char str8[] = "0x887e2561352d80fa";
+static const char str9[] = "614FF7EAA63009DA";
 
 static int str_upper(struct unit_test_state *uts)
 {
@@ -186,6 +188,22 @@
 }
 LIB_TEST(str_hextoul, 0);
 
+static int str_hextoull(struct unit_test_state *uts)
+{
+	char *endp;
+
+	/* Just a simple test, since we know this uses simple_strtoull() */
+	ut_asserteq_64(0x887e2561352d80faULL, hextoull(str8, &endp));
+	ut_asserteq_64(0x12, endp - str8);
+	ut_asserteq_64(0x614ff7eaa63009daULL, hextoull(str9, &endp));
+	ut_asserteq_64(0x10, endp - str9);
+	ut_asserteq_64(0x887e2561352d80faULL, hextoull(str8, NULL));
+	ut_asserteq_64(0x614ff7eaa63009daULL, hextoull(str9, NULL));
+
+	return 0;
+}
+LIB_TEST(str_hextoull, 0);
+
 static int str_dectoul(struct unit_test_state *uts)
 {
 	char *endp;