diff --git a/devbin/make-executable-zip.sh b/devbin/make-executable-zip.sh
index a145ca9..342a20c 100755
--- a/devbin/make-executable-zip.sh
+++ b/devbin/make-executable-zip.sh
@@ -30,8 +30,8 @@ echo 'import px.px; px.px.main()' >"$WORKDIR/__main__.py"
 cp -a "$ROOTDIR/px" "$WORKDIR/"
 
 # Dependencies, must match list in requirements.txt
-cp -a "$ENVDIR"/lib/python*/site-packages/dateutil "$WORKDIR/"
-cp -a "$ENVDIR"/lib/python*/site-packages/six.py "$WORKDIR/"
+#
+# NOTE: This section intentionally left blank
 
 # Tidy up a bit
 find "$WORKDIR" -name '*.pyc' -delete
diff --git a/requirements.txt b/requirements.txt
index 9516d45..1e6774e 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -5,11 +5,5 @@
 # NOTE: If you change something here, you must update make-executable-zip.sh as
 # well, search for "requirements.txt"!
 
-# NOTE: We don't use six ourselves, but python-dateutil does. Do remove once
-# we're on a Python-3-only python-dateutil!
-six
-
-# 2.6.1 is what we started out using, older is probably fine
-# as well but I don't know *how* old. If anybody wants older,
-# let me know and we'll see. /johan.walles@gmail.com 2019mar11
-python-dateutil >= 2.6.1
+# NOTE: This file intentionally left blank because we don't have any third-party
+# runtime dependencies.
\ No newline at end of file
diff --git a/tox.ini b/tox.ini
index 39b3c88..db3fcd4 100644
--- a/tox.ini
+++ b/tox.ini
@@ -82,6 +82,7 @@ depends = version.py ruff-format
 deps =
     pytest == {[tox]pytest_version}
     pytest-avoidance == 0.3.0
+    python-dateutil >= 2.6.1
     -r requirements.txt
 commands =
     pytest --durations=10 --color=yes tests