diff --git a/simgear/scene/material/matlib.cxx b/simgear/scene/material/matlib.cxx
index 6aa82d4e..484e0783 100644
--- a/simgear/scene/material/matlib.cxx
+++ b/simgear/scene/material/matlib.cxx
@@ -175,7 +175,7 @@ SGMaterialLib::~SGMaterialLib ( void ) {
 }
 
 const SGMaterial*
-SGMaterialLib::findMaterial(const osg::StateSet* stateSet) const
+SGMaterialLib::findMaterial(const osg::StateSet* stateSet)
 {
   if (!stateSet)
     return 0;
diff --git a/simgear/scene/material/matlib.hxx b/simgear/scene/material/matlib.hxx
index 94f47881..f1970985 100644
--- a/simgear/scene/material/matlib.hxx
+++ b/simgear/scene/material/matlib.hxx
@@ -83,7 +83,7 @@ public:
     material_map_iterator end() { return matlib.end(); }
     const_material_map_iterator end() const { return matlib.end(); }
 
-    const SGMaterial* findMaterial(const osg::StateSet* stateSet) const;
+    static const SGMaterial* findMaterial(const osg::StateSet* stateSet);
 
     // Destructor
     ~SGMaterialLib ( void );