diff --git a/src/Environment/realwx_ctrl.hxx b/src/Environment/realwx_ctrl.hxx
index 93155e6e8..00ab1947f 100644
--- a/src/Environment/realwx_ctrl.hxx
+++ b/src/Environment/realwx_ctrl.hxx
@@ -24,7 +24,7 @@
 #define _REALWX_CTRL_HXX
 
 #include <simgear/structure/subsystem_mgr.hxx>
-
+#include <simgear/props/props.hxx>
 namespace Environment {
 class RealWxController : public SGSubsystem
 {
diff --git a/src/Instrumentation/dclgps.hxx b/src/Instrumentation/dclgps.hxx
index 11d48bc5e..e2b2ee269 100644
--- a/src/Instrumentation/dclgps.hxx
+++ b/src/Instrumentation/dclgps.hxx
@@ -33,6 +33,7 @@
 #include <map>
 
 #include <simgear/structure/subsystem_mgr.hxx>
+#include <simgear/props/props.hxx>
 #include <Navaids/positioned.hxx>
 
 class SGTime;
diff --git a/src/Main/logger.hxx b/src/Main/logger.hxx
index 1f99cd910..c1b56b264 100644
--- a/src/Main/logger.hxx
+++ b/src/Main/logger.hxx
@@ -11,6 +11,7 @@
 
 #include <simgear/compiler.h>
 #include <simgear/structure/subsystem_mgr.hxx>
+#include <simgear/props/props.hxx>
 
 /**
  * Log any property values to any number of CSV files.
diff --git a/src/Main/viewmgr.hxx b/src/Main/viewmgr.hxx
index c14347e26..6461af11a 100644
--- a/src/Main/viewmgr.hxx
+++ b/src/Main/viewmgr.hxx
@@ -29,6 +29,7 @@
 
 #include <simgear/compiler.h>
 #include <simgear/structure/subsystem_mgr.hxx>
+#include <simgear/props/props.hxx>
 #include <simgear/math/SGMath.hxx>
 
 // forward decls
diff --git a/src/Sound/fg_fx.hxx b/src/Sound/fg_fx.hxx
index 26c802f34..8051ce4aa 100644
--- a/src/Sound/fg_fx.hxx
+++ b/src/Sound/fg_fx.hxx
@@ -29,6 +29,7 @@
 #include <vector>
 
 #include <simgear/structure/subsystem_mgr.hxx>
+#include <simgear/props/props.hxx>
 #include <simgear/sound/sample_group.hxx>
 
 class SGXmlSound;
diff --git a/src/Sound/sample_queue.hxx b/src/Sound/sample_queue.hxx
index db3d9c785..6bbc076ce 100644
--- a/src/Sound/sample_queue.hxx
+++ b/src/Sound/sample_queue.hxx
@@ -29,6 +29,7 @@
 #include <queue>
 
 #include <simgear/structure/subsystem_mgr.hxx>
+#include <simgear/props/props.hxx>
 #include <simgear/sound/sample_group.hxx>
 
 class SGSoundSample;
diff --git a/src/Time/TimeManager.hxx b/src/Time/TimeManager.hxx
index d0dff8155..59aa03616 100644
--- a/src/Time/TimeManager.hxx
+++ b/src/Time/TimeManager.hxx
@@ -22,6 +22,7 @@
 #define FG_TIME_TIMEMANAGER_HXX
 
 #include <simgear/structure/subsystem_mgr.hxx>
+#include <simgear/props/props.hxx>
 
 // forward decls
 class SGTime;