diff --git a/newsfragments/2958.other b/newsfragments/2958.other
new file mode 100644
index 000000000..365e7b9e2
--- /dev/null
+++ b/newsfragments/2958.other
@@ -0,0 +1 @@
+The PyInstaller CI job now works around a pip/pyinstaller incompatibility.
diff --git a/tox.ini b/tox.ini
index c0fc2b56a..22d99325c 100644
--- a/tox.ini
+++ b/tox.ini
@@ -118,6 +118,9 @@ commands =
          sphinx-build -b html -d {toxinidir}/docs/_build/doctrees {toxinidir}/docs {toxinidir}/docs/_build/html
 
 [testenv:pyinstaller]
+# We override this to pass --no-use-pep517 because pyinstaller (3.4, at least)
+# is broken when pep517 rules are followed.
+install_command = python -m pip --no-use-pep517 install {opts} {packages}
 extras =
 deps =
     packaging