diff --git a/tox.ini b/tox.ini
index 2271bd2ac..848454333 100644
--- a/tox.ini
+++ b/tox.ini
@@ -38,6 +38,7 @@ commands =
 [testenv:coverage]
 # coverage (with --branch) takes about 65% longer to run
 commands =
+         pip freeze
          tahoe --version
          coverage run --branch -m twisted.trial {env:TAHOE_LAFS_TRIAL_ARGS:--rterrors --reporter=timing} {posargs:allmydata}
          coverage xml