diff --git a/src/osgVolume/RayTracedTechnique.cpp b/src/osgVolume/RayTracedTechnique.cpp
index 752c210c9..ab0fac8de 100644
--- a/src/osgVolume/RayTracedTechnique.cpp
+++ b/src/osgVolume/RayTracedTechnique.cpp
@@ -319,6 +319,8 @@ void RayTracedTechnique::init()
         else if (shadingModel==Isosurface)
         {
 
+            enableBlending = true;
+
             stateset->addUniform(cpv._isoProperty->getUniform());
 
             if (tf)