diff --git a/tox.ini b/tox.ini
index 28adb28a6..3f39965d2 100644
--- a/tox.ini
+++ b/tox.ini
@@ -38,6 +38,7 @@ commands =
     python igor.py zip_mods
 
     # Build the C extension and test with the CTracer
+    python setup.py --quiet build_ext --inplace
     python -m pip install -q -e .
     python igor.py test_with_tracer c {posargs}