diff --git a/tests/values.cpp b/tests/values.cpp
index daad844f8bd2b80f939e1e8314b6edcf26501f40..6bcaa81bed53a308f193a23273fc9df67041a2bd 100644
--- a/tests/values.cpp
+++ b/tests/values.cpp
@@ -100,6 +100,8 @@ BOOST_AUTO_TEST_CASE(tset_ops)
 	BOOST_CHECK_EQUAL(2, s1.categories_count(tagset));
 	s1.insert_symbol(tagset, "f");
 	BOOST_CHECK_EQUAL(3, s1.categories_count(tagset));
+	s1.insert_symbol(tagset, "adj");
+	BOOST_CHECK_EQUAL(3, s1.categories_count(tagset));
 }
 
 BOOST_AUTO_TEST_CASE(position_ops)