diff --git a/src/osgVolume/Property.cpp b/src/osgVolume/Property.cpp
index 6826b0600..84055926d 100644
--- a/src/osgVolume/Property.cpp
+++ b/src/osgVolume/Property.cpp
@@ -350,7 +350,7 @@ bool PropertyAdjustmentCallback::handle(const osgGA::GUIEventAdapter& ea,osgGA::
             if (_updateTransparency && cpv._transparencyProperty.valid())
             {
                 OSG_INFO<<"Setting transparency to "<<v2<<std::endl;
-                cpv._transparencyProperty->setValue(v2);
+                cpv._transparencyProperty->setValue(1.0f-v2);
             }
 
             if (_updateSampleDensity && cpv._sampleDensityProperty.valid())