diff --git a/docs/subsystems/dependencies.md b/docs/subsystems/dependencies.md
index 8e9da08e7a..9e46cf8bb9 100644
--- a/docs/subsystems/dependencies.md
+++ b/docs/subsystems/dependencies.md
@@ -118,6 +118,12 @@ extension, used by our [full-text search](full-text-search.md).
 
 ## Python packages
 
+Zulip uses the version of Python itself provided by the host OS for
+the Zulip server.  We currently support Python 3.6 and newer, with
+Ubuntu Bionic being the platform requiring 3.6 support. The comments
+in `.github/workflows/zulip-ci.yml` document the Python versions used
+by each supported platform.
+
 We manage Python packages via the Python-standard `requirements.txt`
 system and virtualenvs, but there’s a number of interesting details
 about how Zulip makes this system work well for us that are worth