diff --git a/include/osg/Image b/include/osg/Image
index 96094b50c..23bbcd681 100644
--- a/include/osg/Image
+++ b/include/osg/Image
@@ -135,10 +135,14 @@ class OSG_EXPORT Image : public BufferData
         virtual void readImageFromCurrentTexture(unsigned int contextID, bool copyMipMapsIfAvailable, GLenum type = GL_UNSIGNED_BYTE);
 
 
-        /** Scale image to specified size. */
+        /** Scale image to specified size.
+          * \warning The method uses gluScaleImage() and thus needs a valid rendering context.
+        */
         void scaleImage(int s,int t,int r) { scaleImage(s,t,r, getDataType()); }
 
-        /** Scale image to specified size and with specified data type. */
+        /** Scale image to specified size and with specified data type.
+          * \warning The method uses gluScaleImage() and thus needs a valid rendering context.
+        */
         virtual void scaleImage(int s,int t,int r, GLenum newDataType);
 
         /** Copy a source Image into a subpart of this Image at specified position.
diff --git a/src/osg/Image.cpp b/src/osg/Image.cpp
index 098389107..8bdc91124 100644
--- a/src/osg/Image.cpp
+++ b/src/osg/Image.cpp
@@ -960,9 +960,9 @@ void Image::scaleImage(int s,int t,int r, GLenum newDataType)
     }
     else
     {
-    delete [] newData;
+        delete [] newData;
 
-        notify(WARN) << "Error Image::scaleImage() did not succeed : errorString = "<<gluErrorString((GLenum)status)<<std::endl;
+        notify(WARN) << "Error Image::scaleImage() did not succeed : errorString = "<< gluErrorString((GLenum)status) << ". The rendering context may be invalid." << std::endl;
     }
 
     dirty();
@@ -1023,7 +1023,7 @@ void Image::copySubImage(int s_offset, int t_offset, int r_offset, const osg::Im
 
     if (status!=0)
     {
-        notify(WARN) << "Error Image::scaleImage() do not succeed : errorString = "<<gluErrorString((GLenum)status)<<std::endl;
+        notify(WARN) << "Error Image::scaleImage() did not succeed : errorString = "<< gluErrorString((GLenum)status) << ". The rendering context may be invalid." << std::endl;
     }
 #else
     osg::notify(osg::NOTICE)<<"Warning: Image::copySubImage(int, int, int, const osg::Image*)) not supported."<<std::endl;