diff --git a/.dockerignore b/.dockerignore
index 2ce8a8209..203d8000f 100644
--- a/.dockerignore
+++ b/.dockerignore
@@ -6,6 +6,6 @@
 # test docker on their git working directories.
 
 .git
-.tox
+tox.cover
 venv
 docs
diff --git a/.gitignore b/.gitignore
index 54670e6da..2441f1a74 100644
--- a/.gitignore
+++ b/.gitignore
@@ -4,7 +4,7 @@
 build/
 dist/
 /venv/
-/.tox/
+/tox.venv/
 letsencrypt.log
 
 # coverage
diff --git a/tox.ini b/tox.ini
index 71eb950d1..031f3af4f 100644
--- a/tox.ini
+++ b/tox.ini
@@ -9,6 +9,10 @@ skipsdist = true
 envlist = py26,py27,cover,lint
 
 [testenv]
+# share one venv across testenvs, instead of multiple
+# .tox/{py26,py27,cover,lint}; but do NOT set envdir to
+# {toxinidir}/venv as it will destroy existing dev venv
+envdir = {toxinidir}/tox.venv
 commands =
     pip install -r requirements.txt -e acme -e .[testing] -e letsencrypt_apache -e letsencrypt_nginx
     # -q does not suppress errors