diff --git a/global/classic-zaza/tox.ini b/global/classic-zaza/tox.ini
index 2d6468c..94f0688 100644
--- a/global/classic-zaza/tox.ini
+++ b/global/classic-zaza/tox.ini
@@ -14,19 +14,6 @@ skipsdist = True
 sitepackages = False
 # NOTE: Avoid false positives by not skipping missing interpreters.
 skip_missing_interpreters = False
-# NOTES:
-# * We avoid the new dependency resolver by pinning pip < 20.3, see
-#   https://github.com/pypa/pip/issues/9187
-# * Pinning dependencies requires tox >= 3.2.0, see
-#   https://tox.readthedocs.io/en/latest/config.html#conf-requires
-# * It is also necessary to pin virtualenv as a newer virtualenv would still
-#   lead to fetching the latest pip in the func* tox targets, see
-#   https://stackoverflow.com/a/38133283
-requires =
-  pip < 20.3
-  virtualenv < 20.0
-  setuptools < 50.0.0
-
 # NOTE: https://wiki.canonical.com/engineering/OpenStack/InstallLatestToxOnOsci
 minversion = 3.18.0
 
@@ -39,8 +26,14 @@ install_command =
 commands = stestr run --slowest {posargs}
 allowlist_externals =
     charmcraft
+    {toxinidir}/pip.sh
     rename.sh
-passenv = HOME TERM CS_* OS_* TEST_*
+passenv =
+    HOME
+    TERM
+    CS_*
+    OS_*
+    TEST_*
 deps = -r{toxinidir}/test-requirements.txt
 
 [testenv:build]
diff --git a/global/source-zaza/src/tox.ini b/global/source-zaza/src/tox.ini
index b40d295..ba88759 100644
--- a/global/source-zaza/src/tox.ini
+++ b/global/source-zaza/src/tox.ini
@@ -11,16 +11,6 @@ skipsdist = True
 sitepackages = False
 # NOTE: Avoid false positives by not skipping missing interpreters.
 skip_missing_interpreters = False
-# NOTES:
-# * We avoid the new dependency resolver by pinning pip < 20.3, see
-#   https://github.com/pypa/pip/issues/9187
-# * Pinning dependencies requires tox >= 3.2.0, see
-#   https://tox.readthedocs.io/en/latest/config.html#conf-requires
-# * It is also necessary to pin virtualenv as a newer virtualenv would still
-#   lead to fetching the latest pip in the func* tox targets, see
-#   https://stackoverflow.com/a/38133283
-requires = pip < 20.3
-           virtualenv < 20.0
 # NOTE: https://wiki.canonical.com/engineering/OpenStack/InstallLatestToxOnOsci
 minversion = 3.18.0
 
@@ -28,7 +18,12 @@ minversion = 3.18.0
 setenv = VIRTUAL_ENV={envdir}
          PYTHONHASHSEED=0
 allowlist_externals = juju
-passenv = HOME TERM CS_* OS_* TEST_*
+passenv =
+    HOME
+    TERM
+    CS_*
+    OS_*
+    TEST_*
 deps = -r{toxinidir}/test-requirements.txt
 install_command =
   pip install {opts} {packages}
diff --git a/global/source-zaza/tox.ini b/global/source-zaza/tox.ini
index 713990e..92ce03d 100644
--- a/global/source-zaza/tox.ini
+++ b/global/source-zaza/tox.ini
@@ -11,19 +11,6 @@ envlist = pep8,py3
 sitepackages = False
 # NOTE: Avoid false positives by not skipping missing interpreters.
 skip_missing_interpreters = False
-# NOTES:
-# * We avoid the new dependency resolver by pinning pip < 20.3, see
-#   https://github.com/pypa/pip/issues/9187
-# * Pinning dependencies requires tox >= 3.2.0, see
-#   https://tox.readthedocs.io/en/latest/config.html#conf-requires
-# * It is also necessary to pin virtualenv as a newer virtualenv would still
-#   lead to fetching the latest pip in the func* tox targets, see
-#   https://stackoverflow.com/a/38133283
-requires =
-  pip < 20.3
-  virtualenv < 20.0
-  setuptools<50.0.0
-
 # NOTE: https://wiki.canonical.com/engineering/OpenStack/InstallLatestToxOnOsci
 minversion = 3.18.0
 
@@ -31,16 +18,19 @@ minversion = 3.18.0
 setenv = VIRTUAL_ENV={envdir}
          PYTHONHASHSEED=0
          TERM=linux
-         LAYER_PATH={toxinidir}/layers
-         INTERFACE_PATH={toxinidir}/interfaces
          JUJU_REPOSITORY={toxinidir}/build
-passenv = no_proxy http_proxy https_proxy INTERFACE_PATH LAYER_PATH JUJU_REPOSITORY
+passenv =
+    no_proxy
+    http_proxy
+    https_proxy
+    JUJU_REPOSITORY
 install_command =
   {toxinidir}/pip.sh install {opts} {packages}
 allowlist_externals =
     charmcraft
     bash
     tox
+    {toxinidir}/pip.sh
     rename.sh
 deps =
     -r{toxinidir}/requirements.txt
@@ -94,7 +84,7 @@ changedir = {toxinidir}/src
 commands =
   bash -c "if [ ! -f ../*.charm ]; then echo 'Charm does not exist. Run tox -e build'; exit 1; fi"
   tox --version
-  tox -e func-target {posargs}
+  tox -e func-target -- {posargs}
 
 [testenv:cover]
 # Technique based heavily upon