diff --git a/wheelhouse.txt b/wheelhouse.txt
index 5e9212b..664a385 100644
--- a/wheelhouse.txt
+++ b/wheelhouse.txt
@@ -1,3 +1,6 @@
+# pip is pinned to <19.0 to avoid https://github.com/pypa/pip/issues/6164
+# even with installing setuptools before upgrading pip ends up with pip seeing
+# the older setuptools at the system level if include_system_packages is true
 pip>=18.1,<19.0
 setuptools<42
 setuptools-scm<=1.17.0