diff --git a/simgear/props/propertyObject.cxx b/simgear/props/propertyObject.cxx
index df3f81f9..ff87898e 100644
--- a/simgear/props/propertyObject.cxx
+++ b/simgear/props/propertyObject.cxx
@@ -34,6 +34,13 @@ void PropertyObjectBase::setDefaultRoot(SGPropertyNode* aRoot)
 {
   static_defaultRoot = aRoot;
 }
+  
+PropertyObjectBase::PropertyObjectBase() :
+  _path(NULL),
+  _prop(NULL)
+{
+    
+}
 
 PropertyObjectBase::PropertyObjectBase(const PropertyObjectBase& aOther) :
   _path(aOther._path),
diff --git a/simgear/props/propertyObject.hxx b/simgear/props/propertyObject.hxx
index 5cc1588b..a6d357f8 100644
--- a/simgear/props/propertyObject.hxx
+++ b/simgear/props/propertyObject.hxx
@@ -28,6 +28,8 @@ class PropertyObjectBase
 public:
   static void setDefaultRoot(SGPropertyNode* aRoot);
   
+  PropertyObjectBase();
+  
   PropertyObjectBase(const PropertyObjectBase& aOther);
     
   PropertyObjectBase(const char* aChild);
@@ -57,6 +59,8 @@ template <typename T>
 class PropertyObject : PropertyObjectBase
 {
 public:
+  PropertyObject();
+  
   /**
    * Create from path relative to the default root, and option default value
    */
@@ -220,11 +224,9 @@ private:
 
 } // of namespace simgear
 
-/*
 typedef simgear::PropertyObject<double> SGPropObjDouble;
 typedef simgear::PropertyObject<bool> SGPropObjBool;
 typedef simgear::PropertyObject<std::string> SGPropObjString;
 typedef simgear::PropertyObject<long> SGPropObjInt;
-*/
 
 #endif