diff --git a/daemon_state_interface.h b/daemon_state_interface.h
index a0944aa..2356816 100644
--- a/daemon_state_interface.h
+++ b/daemon_state_interface.h
@@ -20,6 +20,7 @@
 #include "update_engine/service_observer_interface.h"
 
 #include <memory>
+#include <set>
 
 namespace chromeos_update_engine {
 
@@ -36,6 +37,9 @@
   virtual void AddObserver(ServiceObserverInterface* observer) = 0;
   virtual void RemoveObserver(ServiceObserverInterface* observer) = 0;
 
+  // Return the set of current observers.
+  virtual const std::set<ServiceObserverInterface*>& service_observers() = 0;
+
  protected:
   DaemonStateInterface() = default;
 };