diff --git a/rmf_fleet_adapter/src/rmf_fleet_adapter/TaskManager.cpp b/rmf_fleet_adapter/src/rmf_fleet_adapter/TaskManager.cpp
index 326f00704..219ae05e2 100644
--- a/rmf_fleet_adapter/src/rmf_fleet_adapter/TaskManager.cpp
+++ b/rmf_fleet_adapter/src/rmf_fleet_adapter/TaskManager.cpp
@@ -922,6 +922,29 @@ void TaskManager::set_queue(
     {
       return;
     }
+
+    // Cancel pending automatic tasks that will be removed from the new
+    // assignments.
+    std::unordered_set<std::string> new_automatic_task_ids;
+    const std::vector<std::string> cancellation_labels =
+    {"New task assignments received."};
+    for (const auto& a : assignments)
+    {
+      if (a.request()->booking()->automatic())
+      {
+        new_automatic_task_ids.insert(a.request()->booking()->id());
+      }
+    }
+    for (const auto& a : _queue)
+    {
+      if (a.request()->booking()->automatic() &&
+        new_automatic_task_ids.find(a.request()->booking()->id()) ==
+        new_automatic_task_ids.end())
+      {
+        _publish_canceled_pending_task(a, cancellation_labels);
+      }
+    }
+
     _queue = assignments;
     _publish_task_queue();
   }