diff --git a/.coveragerc b/.coveragerc
index 7f5f766..5aa9b01 100644
--- a/.coveragerc
+++ b/.coveragerc
@@ -1,3 +1,5 @@
+# -*- mode: conf -*-
+
 [run]
 # only record trace data for wormhole.*
 source =
diff --git a/src/wormhole/test/run_trial.py b/src/wormhole/test/run_trial.py
new file mode 100644
index 0000000..3a8e743
--- /dev/null
+++ b/src/wormhole/test/run_trial.py
@@ -0,0 +1,16 @@
+
+# This is a tiny helper module, to let "python -m wormhole.test.run_trial
+# ARGS" does the same thing as running "trial ARGS" (unfortunately
+# twisted/scripts/trial.py does not have a '__name__=="__main__"' clause).
+#
+# This makes it easier to run trial under coverage from tox:
+# * "coverage run trial ARGS" is how you'd usually do it
+# * but "trial" must be the one in tox's virtualenv
+# * "coverage run `which trial` ARGS" works from a shell
+# * but tox doesn't use a shell
+# So use:
+#  "coverage run -m wormhole.test.run_trial ARGS"
+
+from twisted.scripts.trial import run
+
+run()
diff --git a/tox.ini b/tox.ini
index 326afa5..e23eb75 100644
--- a/tox.ini
+++ b/tox.ini
@@ -32,3 +32,14 @@ commands =
 # a script name (since "python -m twisted.scripts.trial" doesn't have a 'if
 # __name__ == "__main__": run()' -style clause). The script name will vary on
 # the platform.
+
+[testenv:coverage]
+deps =
+    pyflakes >= 1.2.3
+    mock
+    coverage
+    {env:EXTRA_DEPENDENCY:}
+commands =
+    pyflakes setup.py src
+    wormhole --version
+    coverage run --branch -m wormhole.test.run_trial {posargs:wormhole}