diff --git a/include/osg/Callback b/include/osg/Callback
index ff4c2dca2..61aad35c8 100644
--- a/include/osg/Callback
+++ b/include/osg/Callback
@@ -20,7 +20,7 @@
 namespace osg {
 
 
-class Callback : public virtual Object {
+class OSG_EXPORT Callback : public virtual Object {
 
     public :
 
diff --git a/include/osg/StateSet b/include/osg/StateSet
index f9b076c17..10aa93307 100644
--- a/include/osg/StateSet
+++ b/include/osg/StateSet
@@ -378,7 +378,7 @@ class OSG_EXPORT StateSet : public Object
         inline bool getNestRenderBins() const { return _nestRenderBins; }
 
 
-        struct Callback : public virtual osg::Callback
+        struct OSG_EXPORT Callback : public virtual osg::Callback
         {
             Callback() {}