diff --git a/real_system_state.h b/real_system_state.h
index 7e0c16d..4e97b95 100644
--- a/real_system_state.h
+++ b/real_system_state.h
@@ -47,7 +47,7 @@
 
   inline ClockInterface* clock() override { return &clock_; }
 
-  inline ConnectionManager* connection_manager() override {
+  inline ConnectionManagerInterface* connection_manager() override {
     return &connection_manager_;
   }