diff --git a/tests/test_link.py b/tests/test_link.py
index 9ef85d8..89bb7aa 100644
--- a/tests/test_link.py
+++ b/tests/test_link.py
@@ -139,6 +139,22 @@ class Connecting(unittest.TestCase):
         self.link.work = lambda: 0
         self.assertEqual(self.link.active_device()["alias"], "frame-2")  # idle: move on
 
+    def test_nothing_elsewhere_moves_a_running_install(self):
+        """A bare alias in use, then another server sets up and picks a headset."""
+        self.link.override = None
+        self.hosts({"localhost": "ok"})
+        with mock.patch.object(fl, "ssh_g", return_value=("localhost", self.port, "tester", False)):
+            self.link.connect(["start"])
+        started = self.routes[-1]
+        other = fd.Registry(self.dir / "devices.json")
+        other.set_active(other.add_device("frame-2", hosts=["192.0.2.2"])["id"])
+        self.link.work = lambda: 1
+        with mock.patch.object(fl, "ssh_g", return_value=("localhost", self.port, "tester", False)):
+            self.link.close_master()
+            self.link.connect(["dropped"])
+        self.assertEqual(self.routes[-1][0], started[0])
+        self.assertTrue(self.link.deferred)
+
     def listen6(self):
         """A "different device": the same port on IPv6 loopback."""
         try:
diff --git a/ui/frame_link.py b/ui/frame_link.py
index dba31a5..51979c6 100644
--- a/ui/frame_link.py
+++ b/ui/frame_link.py
@@ -487,11 +487,11 @@ class Link:
                 device = dict(device, user=device.get("user") or u, port=p, frozen_host=h, proxied=proxied, frozen=[
                     "-o", f"HostName={frame_devices.ssh_host(h)}", "-o", f"Port={p}",
                     *(["-o", f"User={u}"] if u else [])])
-            if self.routed and self.routed_device and device["alias"] == self.routed_device["alias"] \
-                    and self.route_key(device) != self.routed and self.work():
-                # Set Up Connection changed this headset in ~/.ssh/config (its login, or a bare
-                # alias became a set-up headset) while an install runs: reconnect as it
-                # started; the change applies once it's done (see watch_config).
+            if self.routed and self.routed_device and self.route_key(device) != self.routed and self.work():
+                # While an install runs, nothing moves it: not Set Up Connection changing this
+                # headset in ~/.ssh/config, nor another Frame Control server adding, choosing
+                # or removing headsets in devices.json. (Switching here is refused meanwhile.)
+                # Reconnect as it started; the change applies once it's done (see watch_config).
                 device = self.routed_device
                 self.deferred = True
             if self.route_key(device) != self.routed: