diff --git a/tox.ini b/tox.ini
index 65355b259..11c02feda 100644
--- a/tox.ini
+++ b/tox.ini
@@ -16,8 +16,8 @@ commands =
     # check that we have the expected Python version and architecture
     {envpython} -c "import sys; print(sys.version)"
     {envpython} -c "import struct; print(struct.calcsize('P') * 8)"
-    # run the test suite
-    py.test {posargs}
+    # run the test suite against the package installed inside tox env
+    py.test {posargs:--pyargs fontTools}
 
 [testenv:coveralls]
 passenv = TRAVIS TRAVIS_JOB_ID TRAVIS_BRANCH