diff --git a/docs/backends/slack.rst b/docs/backends/slack.rst
index 615912bf..eea4cb99 100644
--- a/docs/backends/slack.rst
+++ b/docs/backends/slack.rst
@@ -33,9 +33,17 @@ Slack
 
   See auth scopes at `Slack OAuth docs`_.
 
-- Limiting by team is possible by::
+- To allow sign-in only from one Slack workspace, set its workspace ID::
 
-    SOCIAL_AUTH_SLACK_TEAM = ''
+    SOCIAL_AUTH_SLACK_TEAM = 'T0123456789'
+
+  The backend checks the ``team.id`` returned by Slack's ``users.identity``
+  response before signing in. The ``team`` authorization parameter selects a
+  workspace on Slack's sign-in page, but does not enforce this restriction.
+  A missing or different workspace ID rejects the sign-in. Configure a
+  workspace ID (starting with ``T``), not a workspace name or Enterprise
+  organization ID (starting with ``E``). Deployments previously using a name
+  or organization ID must update this setting before upgrading.
 
 .. _Slack: https://api.slack.com/applications
 .. _Slack OAuth docs: https://api.slack.com/docs/oauth