diff --git a/tox.ini b/tox.ini
index 912fc817..0fe8da44 100644
--- a/tox.ini
+++ b/tox.ini
@@ -53,6 +53,7 @@ extras =
     test
 deps =
     xdist: pytest-xdist
+    cov: pytest-cov
     jwst: jwst[test] @ git+https://github.com/spacetelescope/jwst.git
     romancal: romancal[test] @ git+https://github.com/spacetelescope/romancal.git
     numpy120: numpy==1.20.*