diff --git a/tests/fixtures/layouts/reconfigure-window-fixed.yaml b/tests/fixtures/layouts/reconfigure-window-fixed.yaml
new file mode 100644
index 0000000..9aa1a97
--- /dev/null
+++ b/tests/fixtures/layouts/reconfigure-window-fixed.yaml
@@ -0,0 +1,46 @@
+- pipeline:
+    name: gate
+    manager: dependent
+    trigger:
+      gerrit:
+        - event: comment-added
+          approval:
+            - Approved: 1
+    start:
+      gerrit:
+        Verified: 0
+    success:
+      gerrit:
+        Verified: 2
+        submit: true
+    failure:
+      gerrit:
+        Verified: -2
+    window: 2
+    window-increase-type: exponential
+    window-increase-factor: 1
+    window-decrease-type: exponential
+    window-decrease-factor: 1
+
+- job:
+    name: base
+    parent: null
+    nodeset:
+      nodes:
+        - label: ubuntu-xenial
+          name: controller
+
+- job:
+    name: job1
+    run: playbooks/job1.yaml
+
+- job:
+    name: job2
+    run: playbooks/job2.yaml
+
+- project:
+    name: org/project
+    gate:
+      jobs:
+        - job1
+        - job2
diff --git a/tests/fixtures/layouts/reconfigure-window-fixed2.yaml b/tests/fixtures/layouts/reconfigure-window-fixed2.yaml
new file mode 100644
index 0000000..13382c5
--- /dev/null
+++ b/tests/fixtures/layouts/reconfigure-window-fixed2.yaml
@@ -0,0 +1,46 @@
+- pipeline:
+    name: gate
+    manager: dependent
+    trigger:
+      gerrit:
+        - event: comment-added
+          approval:
+            - Approved: 1
+    start:
+      gerrit:
+        Verified: 0
+    success:
+      gerrit:
+        Verified: 2
+        submit: true
+    failure:
+      gerrit:
+        Verified: -2
+    window: 1
+    window-increase-type: exponential
+    window-increase-factor: 1
+    window-decrease-type: exponential
+    window-decrease-factor: 1
+
+- job:
+    name: base
+    parent: null
+    nodeset:
+      nodes:
+        - label: ubuntu-xenial
+          name: controller
+
+- job:
+    name: job1
+    run: playbooks/job1.yaml
+
+- job:
+    name: job2
+    run: playbooks/job2.yaml
+
+- project:
+    name: org/project
+    gate:
+      jobs:
+        - job1
+        - job2
diff --git a/tests/unit/test_scheduler.py b/tests/unit/test_scheduler.py
index 264883c..cad557e 100755
--- a/tests/unit/test_scheduler.py
+++ b/tests/unit/test_scheduler.py
@@ -3879,8 +3879,60 @@
         self.sched.reconfigure(self.config)
         tenant = self.sched.abide.tenants.get('tenant-one')
         queue = tenant.layout.pipelines['gate'].queues[0]
+        # Even though we have configured a smaller window, the value
+        # on the existing shared queue should be used.
+        self.assertEqual(queue.window, 20)
+        self.assertTrue(len(self.builds), 4)
+
+        self.sched.reconfigure(self.config)
+        tenant = self.sched.abide.tenants.get('tenant-one')
+        queue = tenant.layout.pipelines['gate'].queues[0]
+        self.assertEqual(queue.window, 20)
+        self.assertTrue(len(self.builds), 4)
+
+        self.executor_server.hold_jobs_in_build = False
+        self.executor_server.release()
+
+        self.waitUntilSettled()
+        self.assertHistory([
+            dict(name='job1', result='SUCCESS', changes='1,1'),
+            dict(name='job1', result='SUCCESS', changes='1,1 2,1'),
+            dict(name='job2', result='SUCCESS', changes='1,1'),
+            dict(name='job2', result='SUCCESS', changes='1,1 2,1'),
+        ], ordered=False)
+
+    @simple_layout('layouts/reconfigure-window-fixed.yaml')
+    def test_reconfigure_window_fixed(self):
+        # Test the active window shrinking during reconfiguration
+        self.executor_server.hold_jobs_in_build = True
+
+        A = self.fake_gerrit.addFakeChange('org/project', 'master', 'A')
+        A.addApproval('Code-Review', 2)
+        self.fake_gerrit.addEvent(A.addApproval('Approved', 1))
+        self.waitUntilSettled()
+        B = self.fake_gerrit.addFakeChange('org/project', 'master', 'B')
+        B.addApproval('Code-Review', 2)
+        self.fake_gerrit.addEvent(B.addApproval('Approved', 1))
+        self.waitUntilSettled()
+
+        tenant = self.sched.abide.tenants.get('tenant-one')
+        queue = tenant.layout.pipelines['gate'].queues[0]
+        self.assertEqual(queue.window, 2)
+        self.assertTrue(len(self.builds), 4)
+
+        self.executor_server.release('job1')
+        self.waitUntilSettled()
+        self.commitConfigUpdate('org/common-config',
+                                'layouts/reconfigure-window-fixed2.yaml')
+        self.sched.reconfigure(self.config)
+        tenant = self.sched.abide.tenants.get('tenant-one')
+        queue = tenant.layout.pipelines['gate'].queues[0]
+        # Because we have configured a static window, it should
+        # be allowed to shrink on reconfiguration.
         self.assertEqual(queue.window, 1)
-        # B is now outside the window, but builds haven't been canceled
+        # B is outside the window, but still marked active until the
+        # next pass through the queue processor, so its builds haven't
+        # been canceled.
         self.assertTrue(len(self.builds), 4)
 
         self.sched.reconfigure(self.config)
@@ -3892,7 +3944,9 @@
 
         self.executor_server.hold_jobs_in_build = False
         self.executor_server.release()
-        # This will run new builds for B
+
+        # B's builds will be restarted and will show up in our history
+        # twice.
         self.waitUntilSettled()
         self.assertHistory([
             dict(name='job1', result='SUCCESS', changes='1,1'),
diff --git a/zuul/scheduler.py b/zuul/scheduler.py
index 846242c..7dee00d 100644
--- a/zuul/scheduler.py
+++ b/zuul/scheduler.py
@@ -595,10 +595,32 @@
                                  "when reconfiguring" % name)
                 continue
             self.log.debug("Re-enqueueing changes for pipeline %s" % name)
+            # TODO(jeblair): This supports an undocument and
+            # unanticipated hack to create a static window.  If we
+            # really want to support this, maybe we should have a
+            # 'static' type?  But it may be in use in the wild, so we
+            # should allow this at least until there's an upgrade
+            # path.
+            if (new_pipeline.window and
+                new_pipeline.window_increase_type == 'exponential' and
+                new_pipeline.window_decrease_type == 'exponential' and
+                new_pipeline.window_increase_factor == 1 and
+                new_pipeline.window_decrease_factor == 1):
+                static_window = True
+            else:
+                static_window = False
+            if old_pipeline.window and (not static_window):
+                new_pipeline.window = max(old_pipeline.window,
+                                          new_pipeline.window_floor)
             items_to_remove = []
             builds_to_cancel = []
             last_head = None
             for shared_queue in old_pipeline.queues:
+                # Attempt to keep window sizes from shrinking where possible
+                new_queue = new_pipeline.getQueue(shared_queue.projects[0])
+                if new_queue and shared_queue.window and (not static_window):
+                    new_queue.window = max(shared_queue.window,
+                                           new_queue.window_floor)
                 for item in shared_queue.queue:
                     if not item.item_ahead:
                         last_head = item