diff --git a/src/osgPlugins/txp/TrPageArchive.cpp b/src/osgPlugins/txp/TrPageArchive.cpp
index 6dfb147d4..42996e1f5 100644
--- a/src/osgPlugins/txp/TrPageArchive.cpp
+++ b/src/osgPlugins/txp/TrPageArchive.cpp
@@ -233,7 +233,7 @@ void TrPageArchive::LoadMaterials()
                 
                 int alphaFunc;
                 mat->GetAlphaFunc(alphaFunc);
-                if( alphaFunc != trpgMaterial::None)
+                if( alphaFunc>=GL_NEVER && alphaFunc<=GL_ALWAYS)
                 {
                     float64 ref;
                     mat->GetAlphaRef(ref);
diff --git a/src/osgPlugins/txp/TrPageParser.cpp b/src/osgPlugins/txp/TrPageParser.cpp
index f75f33ec9..b20ffde41 100644
--- a/src/osgPlugins/txp/TrPageParser.cpp
+++ b/src/osgPlugins/txp/TrPageParser.cpp
@@ -761,7 +761,7 @@ void TrPageParser::LoadLocalMaterials()
         */
             int alphaFunc;
             mat->GetAlphaFunc(alphaFunc);
-            if( alphaFunc != trpgMaterial::None)
+            if( alphaFunc>=GL_NEVER && alphaFunc<=GL_ALWAYS)
             {
                 float64 ref;
                 mat->GetAlphaRef(ref);