diff --git a/tests/test-is-public-builtin.c b/tests/test-is-public-builtin.c
index 3c9e5f4..ffcac12 100644
--- a/tests/test-is-public-builtin.c
+++ b/tests/test-is-public-builtin.c
@@ -78,6 +78,10 @@ static void test_psl(void)
 		{ ".forgot.his.name", 1 },
 		{ "whoever.his.name", 0 },
 		{ "whoever.forgot.his.name", 0 },
+		{ ".", 1 }, /* special case */
+		{ "", 1 },  /* special case */
+		{ NULL, 1 },  /* special case */
+		{ "adfhoweirh", 1 }, /* unknown TLD */
 	};
 	unsigned it;
 	const psl_ctx_t *psl;
diff --git a/tests/test-is-public.c b/tests/test-is-public.c
index d4a2c28..1f3b8b3 100644
--- a/tests/test-is-public.c
+++ b/tests/test-is-public.c
@@ -76,6 +76,10 @@ static void test_psl(void)
 		{ ".forgot.his.name", 1 },
 		{ "whoever.his.name", 0 },
 		{ "whoever.forgot.his.name", 0 },
+		{ ".", 1 }, /* special case */
+		{ "", 1 },  /* special case */
+		{ NULL, 1 },  /* special case */
+		{ "adfhoweirh", 1 }, /* unknown TLD */
 	};
 	unsigned it;
 	psl_ctx_t *psl;