diff --git a/src/calibre/test_build.py b/src/calibre/test_build.py
index d6a71cc361..2c32c24a6c 100644
--- a/src/calibre/test_build.py
+++ b/src/calibre/test_build.py
@@ -158,6 +158,10 @@ class BuildTest(unittest.TestCase):
         from calibre.utils.certgen import create_key_pair
         create_key_pair()
 
+    def test_fonttools(self):
+        from fontTools.subset import main
+        main
+
     def test_msgpack(self):
         from calibre.utils.date import utcnow
         from calibre.utils.serialize import msgpack_dumps, msgpack_loads