diff --git a/doc/source/admin/components.rst b/doc/source/admin/components.rst
index fc02d79dac..c5427888c5 100644
--- a/doc/source/admin/components.rst
+++ b/doc/source/admin/components.rst
@@ -143,10 +143,6 @@ The following sections of ``zuul.conf`` are used by all Zuul components:
       If present, this will be prefixed to all of the keys before
       transmitting to the statsd server.
 
-.. NOTE: this is a white lie at this point, since only the scheduler
-   uses this, however, we expect other components to use it later, so
-   it's reasonable for admins to plan for this now.
-
 .. attr:: zookeeper
 
    Client connection information for ZooKeeper
diff --git a/releasenotes/notes/zookeeper-hosts-4dd0d7c49f3df206.yaml b/releasenotes/notes/zookeeper-hosts-4dd0d7c49f3df206.yaml
new file mode 100644
index 0000000000..e6747c7d96
--- /dev/null
+++ b/releasenotes/notes/zookeeper-hosts-4dd0d7c49f3df206.yaml
@@ -0,0 +1,6 @@
+---
+upgrade:
+  - The ``hosts`` value in the ``[zookeeper]`` configuration section
+    previously defaulted to ``localhost:2181``, but now is unset by
+    default.  This value is required and must be explicitly set (and
+    the documentation has always indicated this).
diff --git a/zuul/cmd/scheduler.py b/zuul/cmd/scheduler.py
index 785d6078fb..67484bf871 100755
--- a/zuul/cmd/scheduler.py
+++ b/zuul/cmd/scheduler.py
@@ -137,8 +137,9 @@ class Scheduler(zuul.cmd.ZuulDaemonApp):
         nodepool = zuul.nodepool.Nodepool(self.sched)
 
         zookeeper = zuul.zk.ZooKeeper()
-        zookeeper_hosts = get_default(self.config, 'zookeeper',
-                                      'hosts', '127.0.0.1:2181')
+        zookeeper_hosts = get_default(self.config, 'zookeeper', 'hosts', None)
+        if not zookeeper_hosts:
+            raise Exception("The zookeeper hosts config value is required")
         zookeeper_timeout = float(get_default(self.config, 'zookeeper',
                                               'session_timeout', 10.0))
 
diff --git a/zuul/cmd/web.py b/zuul/cmd/web.py
index ed6b12b0fb..b974a756ec 100755
--- a/zuul/cmd/web.py
+++ b/zuul/cmd/web.py
@@ -65,7 +65,9 @@ class WebServer(zuul.cmd.ZuulDaemonApp):
                 sys.exit(1)
 
         params["zk_hosts"] = get_default(
-            self.config, 'zookeeper', 'hosts', '127.0.0.1:2181')
+            self.config, 'zookeeper', 'hosts', None)
+        if not params["zk_hosts"]:
+            raise Exception("The zookeeper hosts config value is required")
 
         try:
             self.web = zuul.web.ZuulWeb(**params)