diff --git a/src/Network/native_ctrls.hxx b/src/Network/native_ctrls.hxx
index 5aab04321..ca4fdb328 100644
--- a/src/Network/native_ctrls.hxx
+++ b/src/Network/native_ctrls.hxx
@@ -34,7 +34,7 @@
 #if FG_HAVE_DDS
 #include "DDS/dds_ctrls.h"
 #else
-using FG_DDS_Ctrls = int;
+using FG_DDS_Ctrls = FGNetCtrls;
 #endif
 
 using std::string;
@@ -66,11 +66,11 @@ public:
 
 // Populate the FGNetCtrls/FG_DDS_Ctrls structure from the property tree.
 template<typename T>
-void FGProps2Ctrls( T *net, bool honor_freezes, bool net_byte_order ) {};
+void FGProps2Ctrls( T *net, bool honor_freezes, bool net_byte_order );
 
 // Update the property tree from the FGNetCtrls/FG_DDS_Ctrls structure.
 template<typename T>
-void FGCtrls2Props( T *net, bool honor_freezes, bool net_byte_order ) {};
+void FGCtrls2Props( T *net, bool honor_freezes, bool net_byte_order );
 
 #endif // _FG_NATIVE_CTRLS_HXX
 
diff --git a/src/Network/native_fdm.hxx b/src/Network/native_fdm.hxx
index 0833d973c..6656d5ac1 100644
--- a/src/Network/native_fdm.hxx
+++ b/src/Network/native_fdm.hxx
@@ -34,7 +34,7 @@
 #if FG_HAVE_DDS
 #include "DDS/dds_fdm.h"
 #else
-using FG_DDS_FDM = int;
+using FG_DDS_FDM = FGNetFDM;
 #endif
 
 
@@ -65,11 +65,11 @@ public:
 
 // Populate the FGNetFDM/FG_DDS_FDM structure from the property tree.
 template<typename T>
-void FGProps2FDM( T *net, bool net_byte_order = true ) {};
+void FGProps2FDM( T *net, bool net_byte_order = true );
 
 // Update the property tree from the FGNetFDM/FG_DDS_FDM structure.
 template<typename T>
-void FGFDM2Props( T *net, bool net_byte_order = true ) {};
+void FGFDM2Props( T *net, bool net_byte_order = true );
 
 #endif // _FG_NATIVE_FDM_HXX
 
diff --git a/src/Network/native_gui.hxx b/src/Network/native_gui.hxx
index f5062569d..6788f6d68 100644
--- a/src/Network/native_gui.hxx
+++ b/src/Network/native_gui.hxx
@@ -32,7 +32,7 @@
 #if FG_HAVE_DDS
 #include "DDS/dds_gui.h"
 #else
-using FG_DDS_GUI = int;
+using FG_DDS_GUI = FGNetGUI;
 #endif
 
 class FGNativeGUI : public FGProtocol {
@@ -62,11 +62,11 @@ public:
 
 // Populate the FGNetGUI/FG_DDS_GUI structure from the property tree.
 template<typename T>
-void FGProps2GUI( T *net ) {};
+void FGProps2GUI( T *net );
 
 // Update the property tree from the FGNetGUI/FG_DDS_GUI structure.
 template<typename T>
-void FGGUI2Props( T *net ) {};
+void FGGUI2Props( T *net );
 
 
 #endif // _FG_NATIVE_GUI_HXX