diff --git a/include/osgViewer/api/X11/PixelBufferX11 b/include/osgViewer/api/X11/PixelBufferX11
index ee8f93115d7..e015e91578f 100644
--- a/include/osgViewer/api/X11/PixelBufferX11
+++ b/include/osgViewer/api/X11/PixelBufferX11
@@ -27,6 +27,11 @@
 #include <X11/X.h>
 #include <GL/glx.h>
 
+#ifndef GLX_VERSION_1_3
+    typedef XID GLXPbuffer;
+#endif
+
+
 namespace osgViewer
 {
 
@@ -34,37 +39,7 @@ class OSGVIEWER_EXPORT PixelBufferX11 : public osg::GraphicsContext
 {
     public:
 
-        PixelBufferX11(osg::GraphicsContext::Traits* traits):
-            _valid(false),
-            _display(0),
-            _parent(0),
-            _pbuffer(0),
-            _visualInfo(0),
-            _glxContext(0),
-            _initialized(false),
-            _realized(false)
-        {
-            _traits = traits;
-
-            init();
-            
-            if (valid())
-            {
-                setState( new osg::State );
-                getState()->setGraphicsContext(this);
-
-                if (_traits.valid() && _traits->sharedContext)
-                {
-                    getState()->setContextID( _traits->sharedContext->getState()->getContextID() );
-                    incrementContextIDUsageCount( getState()->getContextID() );   
-                }
-                else
-                {
-                    getState()->setContextID( osg::GraphicsContext::createNewContextID() );
-                }
-
-            }
-        }
+        PixelBufferX11(osg::GraphicsContext::Traits* traits);
     
         virtual bool isSameKindAs(const Object* object) const { return dynamic_cast<const PixelBufferX11*>(object)!=0; }
         virtual const char* libraryName() const { return "osgViewer"; }
diff --git a/src/osgViewer/GraphicsWindowX11.cpp b/src/osgViewer/GraphicsWindowX11.cpp
index 7c72c82b5a8..4e052778ab1 100644
--- a/src/osgViewer/GraphicsWindowX11.cpp
+++ b/src/osgViewer/GraphicsWindowX11.cpp
@@ -516,7 +516,7 @@ void GraphicsWindowX11::init()
     else
     {
         PixelBufferX11* pixelBufferX11 = dynamic_cast<PixelBufferX11*>(_traits->sharedContext);
-        if (pixelBufferX11)
+        if (pixelBufferX11 && pixelBufferX11->valid())
         {
             sharedContextGLX = pixelBufferX11->getGLXContext();
         }
diff --git a/src/osgViewer/PixelBufferX11.cpp b/src/osgViewer/PixelBufferX11.cpp
index 1e2022c38ff..c743f12b547 100644
--- a/src/osgViewer/PixelBufferX11.cpp
+++ b/src/osgViewer/PixelBufferX11.cpp
@@ -25,9 +25,10 @@
 
 using namespace osgViewer;
 
+#ifdef GLX_VERSION_1_3
 static GLXFBConfig getFBConfigFromVisual(::Display* dpy, XVisualInfo* visualInfo)
 {
-#if defined(__APPLE__) || defined(_AIX)
+#if defined(__APPLE__) || defined(_AIX) || defined(__hpux)
     int screen = visualInfo->screen;
     int nelements;
     GLXFBConfig *configs = glXGetFBConfigs(dpy, screen, &nelements);
@@ -45,12 +46,46 @@ static GLXFBConfig getFBConfigFromVisual(::Display* dpy, XVisualInfo* visualInfo
     return glXGetFBConfigFromVisualSGIX( dpy, visualInfo );
 #endif
 }
+#endif
+
+PixelBufferX11::PixelBufferX11(osg::GraphicsContext::Traits* traits)
+  : _valid(false),
+    _display(0),
+    _parent(0),
+    _pbuffer(0),
+    _visualInfo(0),
+    _glxContext(0),
+    _initialized(false),
+    _realized(false)
+{
+    _traits = traits;
+
+    init();
+    
+    if (valid())
+    {
+        setState( new osg::State );
+        getState()->setGraphicsContext(this);
+
+        if (_traits.valid() && _traits->sharedContext)
+        {
+            getState()->setContextID( _traits->sharedContext->getState()->getContextID() );
+            incrementContextIDUsageCount( getState()->getContextID() );   
+        }
+        else
+        {
+            getState()->setContextID( osg::GraphicsContext::createNewContextID() );
+        }
+
+    }
+}
 
 PixelBufferX11::~PixelBufferX11()
 {
     close(true);
 }
 
+#ifdef GLX_VERSION_1_3
 bool PixelBufferX11::createVisualInfo()
 {
     typedef std::vector<int> Attributes;
@@ -93,8 +128,6 @@ void PixelBufferX11::init()
 {
     if (_initialized) return;
 
-#ifdef GLX_VERSION_1_3
-
     if (!_traits)
     {
         _valid = false;
@@ -232,13 +265,23 @@ void PixelBufferX11::init()
 
     _valid = true;
     _initialized = true;
-#else    
-    _valid = false;
-    _initialized = true;
-    return;
-#endif
 }
 
+#else
+
+// fallback for non GLX1.3 versions where pbuffers are not supported.
+// note, this makes the rest of the pbuffer code a non op as init is false;
+bool PixelBufferX11::createVisualInfo()
+{
+    return false;
+}
+
+void PixelBufferX11::init()
+{
+}
+
+#endif
+
 bool PixelBufferX11::realizeImplementation()
 {
     if (_realized)
@@ -310,9 +353,7 @@ void PixelBufferX11::closeImplementation()
     
         if (_pbuffer)
         {
-#ifdef GLX_VERSION_1_3
             glXDestroyPbuffer(_display, _pbuffer);
-#endif
         }
 
         XFlush( _display );
@@ -347,5 +388,5 @@ void PixelBufferX11::swapBuffersImplementation()
 
     // osg::notify(osg::NOTICE)<<"PixelBufferX11::swapBuffersImplementation "<<this<<" "<<OpenThreads::Thread::CurrentThread()<<std::endl;
 
-    glXSwapBuffers(_display, _pbuffer); 
+    glXSwapBuffers(_display, _pbuffer);
 }