diff --git a/.gitignore b/.gitignore
index 65a48c7..9703f16 100644
--- a/.gitignore
+++ b/.gitignore
@@ -4,6 +4,7 @@
 .test
 .testrepository
 .tox
+.venv
 AUTHORS
 build/*
 ChangeLog
diff --git a/tests/fixtures/layout-merge-queues.yaml b/tests/fixtures/layout-merge-queues.yaml
new file mode 100644
index 0000000..be39a1c
--- /dev/null
+++ b/tests/fixtures/layout-merge-queues.yaml
@@ -0,0 +1,25 @@
+pipelines:
+  - name: gate
+    manager: DependentPipelineManager
+    precedence: low
+    trigger:
+      gerrit:
+        - event: comment-added
+          approval:
+            - approved: 1
+
+projects:
+  - name: projectA
+    gate:
+      - test-only-a
+      - common-test1
+
+  - name: projectB
+    gate:
+      - test-only-b
+      - common-test2
+
+  - name: projectC
+    gate:
+      - common-test1
+      - common-test2
diff --git a/tests/test_scheduler.py b/tests/test_scheduler.py
index 63ab94f..91d0913 100755
--- a/tests/test_scheduler.py
+++ b/tests/test_scheduler.py
@@ -2757,6 +2757,13 @@
         self.assertIn('project-test1', status_jobs)
         self.assertIn('project-test2', status_jobs)
 
+    def test_merging_queues(self):
+        "Test that transitively-connected change queues are merged"
+        self.config.set('zuul', 'layout_config',
+                        'tests/fixtures/layout-merge-queues.yaml')
+        self.sched.reconfigure(self.config)
+        self.assertEqual(len(self.sched.layout.pipelines['gate'].queues), 1)
+
     def test_node_label(self):
         "Test that a job runs on a specific node label"
         self.worker.registerFunction('build:node-project-test1:debian')
diff --git a/zuul/model.py b/zuul/model.py
index 9a076d6..b71552d 100644
--- a/zuul/model.py
+++ b/zuul/model.py
@@ -72,7 +72,7 @@
         return job_tree
 
     def getProjects(self):
-        return self.job_trees.keys()
+        return sorted(self.job_trees.keys(), lambda a, b: cmp(a.name, b.name))
 
     def addQueue(self, queue):
         self.queues.append(queue)
diff --git a/zuul/scheduler.py b/zuul/scheduler.py
index 28e7eb1..ea7f61f 100644
--- a/zuul/scheduler.py
+++ b/zuul/scheduler.py
@@ -1373,6 +1373,21 @@
             change_queues.append(change_queue)
             self.log.debug("Created queue: %s" % change_queue)
 
+        # Iterate over all queues trying to combine them, and keep doing
+        # so until they can not be combined further.
+        last_change_queues = change_queues
+        while True:
+            new_change_queues = self.combineChangeQueues(last_change_queues)
+            if len(last_change_queues) == len(new_change_queues):
+                break
+            last_change_queues = new_change_queues
+
+        self.log.info("  Shared change queues:")
+        for queue in new_change_queues:
+            self.pipeline.addQueue(queue)
+            self.log.info("    %s" % queue)
+
+    def combineChangeQueues(self, change_queues):
         self.log.debug("Combining shared queues")
         new_change_queues = []
         for a in change_queues:
@@ -1386,11 +1401,7 @@
             if not merged_a:
                 self.log.debug("Keeping queue %s" % (a))
                 new_change_queues.append(a)
-
-        self.log.info("  Shared change queues:")
-        for queue in new_change_queues:
-            self.pipeline.addQueue(queue)
-            self.log.info("    %s" % queue)
+        return new_change_queues
 
     def isChangeReadyToBeEnqueued(self, change):
         if not self.pipeline.trigger.canMerge(change,