diff --git a/simgear/structure/subsystem_mgr.cxx b/simgear/structure/subsystem_mgr.cxx
index da180d5b..ac46eeab 100644
--- a/simgear/structure/subsystem_mgr.cxx
+++ b/simgear/structure/subsystem_mgr.cxx
@@ -167,6 +167,8 @@ std::string SGSubsystem::nameForState(State s)
     case State::SUSPEND: return "suspend";
     case State::RESUME: return "resume";
     }
+
+	return {};
 }
 
 ////////////////////////////////////////////////////////////////////////
diff --git a/simgear/structure/subsystem_mgr.hxx b/simgear/structure/subsystem_mgr.hxx
index 6b9d5888..26674a02 100644
--- a/simgear/structure/subsystem_mgr.hxx
+++ b/simgear/structure/subsystem_mgr.hxx
@@ -28,6 +28,7 @@
 #include <string>
 #include <map>
 #include <vector>
+#include <functional>
 
 #include <simgear/timing/timestamp.hxx>
 #include <simgear/structure/SGSharedPtr.hxx>
diff --git a/simgear/structure/subsystem_test.cxx b/simgear/structure/subsystem_test.cxx
index fb27a664..cb07e902 100644
--- a/simgear/structure/subsystem_test.cxx
+++ b/simgear/structure/subsystem_test.cxx
@@ -1,6 +1,7 @@
 #include <simgear_config.h>
 
 #include <cstdio>
+#include <algorithm>
 
 #include <simgear/compiler.h>
 #include <simgear/constants.h>