diff --git a/tox.ini b/tox.ini
index 3125548f4..e42958b28 100644
--- a/tox.ini
+++ b/tox.ini
@@ -218,9 +218,7 @@ extras =
 deps =
     {[testenv]deps}
     packaging
-    # PyInstaller 4.0 drops Python 2 support.  When we finish porting to
-    # Python 3 we can reconsider this constraint.
-    pyinstaller < 4.0
+    pyinstaller
     pefile ; platform_system == "Windows"
 # Setting PYTHONHASHSEED to a known value assists with reproducible builds.
 # See https://pyinstaller.readthedocs.io/en/stable/advanced-topics.html#creating-a-reproducible-build