diff --git a/bindings/python/mapnik_symbolizer.cpp b/bindings/python/mapnik_symbolizer.cpp
index a849ddc1c..509c94d88 100644
--- a/bindings/python/mapnik_symbolizer.cpp
+++ b/bindings/python/mapnik_symbolizer.cpp
@@ -45,74 +45,81 @@ using mapnik::markers_symbolizer;
 struct get_symbolizer_type : public boost::static_visitor<std::string>
 {
 public:
-    get_symbolizer_type() {}
-
-    std::string operator () ( const  point_symbolizer & /*sym*/ )
-    {
-        return "point";
-    }
-
-    std::string operator () ( const line_symbolizer & /*sym*/ )
-    {
-        return "line";
-    }
-
-    std::string operator () ( const line_pattern_symbolizer & /*sym*/ )
-    {
-        return "line_pattern";
-    }
-
-    std::string operator () ( const polygon_symbolizer & /*sym*/ )
-    {
-        return "polygon";
-    }
-
-    std::string operator () ( const polygon_pattern_symbolizer & /*sym*/ )
-    {
-        return "polygon_pattern";
-    }
-
-    std::string operator () ( const raster_symbolizer & /*sym*/ )
-    {
-        return "raster";
-    }
-
-    std::string operator () ( const shield_symbolizer & /*sym*/ )
-    {
-        return "shield";
-    }
-
-    std::string operator () ( const text_symbolizer & /*sym*/ )
-    {
-        return "text";
-    }
-
-    std::string operator () ( const building_symbolizer & /*sym*/ )
-    {
-        return "building";
-    }
-
-    std::string operator () ( const markers_symbolizer & /*sym*/ )
-    {
-        return "markers";
-    }
- 
-    template <typename Symbolizer>
-    std::string operator() ( Symbolizer const& sym)
+    std::string operator () (point_symbolizer const& sym) const
     {
         boost::ignore_unused_variable_warning(sym);
-        return "unknown";
+        return std::string("point");
+    }
+
+    std::string operator () ( line_symbolizer const& sym) const
+    {
+        boost::ignore_unused_variable_warning(sym);
+        return std::string("line");
+    }
+
+    std::string operator () (line_pattern_symbolizer const& sym) const
+    {
+        boost::ignore_unused_variable_warning(sym);
+        return std::string("line_pattern");
+    }
+
+    std::string operator () (polygon_symbolizer const& sym ) const
+    {
+        boost::ignore_unused_variable_warning(sym);
+        return std::string("polygon");
+    }
+
+    std::string operator () (polygon_pattern_symbolizer const& sym) const
+    {
+        boost::ignore_unused_variable_warning(sym);
+        return std::string("polygon_pattern");
+    }
+
+    std::string operator () (raster_symbolizer const& sym) const
+    {
+        boost::ignore_unused_variable_warning(sym);
+        return std::string("raster");
+    }
+
+    std::string operator () (shield_symbolizer const& sym) const
+    {
+        boost::ignore_unused_variable_warning(sym);
+        return std::string("shield");
+    }
+
+    std::string operator () (text_symbolizer const& sym) const
+    {
+        boost::ignore_unused_variable_warning(sym);
+        return std::string("text");
+    }
+
+    std::string operator () (building_symbolizer const& sym) const
+    {
+        boost::ignore_unused_variable_warning(sym);
+        return std::string("building");
+    }
+
+    std::string operator () (markers_symbolizer const& sym) const
+    {
+        boost::ignore_unused_variable_warning(sym);
+        return std::string("markers");
+    }
+
+    template <typename Symbolizer>
+    std::string operator() ( Symbolizer const& sym) const
+    {
+        boost::ignore_unused_variable_warning(sym);
+        return std::string("unknown");
     }
 };
 
-std::string get_symbol_type(const symbolizer& symbol)
+std::string get_symbol_type(symbolizer const& symbol)
 {
-    get_symbolizer_type serializer;
-    std::string type = boost::apply_visitor( serializer, symbol );
+    std::string type = boost::apply_visitor( get_symbolizer_type(), symbol);
     return type;
 }
 
-const point_symbolizer& point_( const symbolizer& symbol )
+const point_symbolizer& point_(symbolizer const& symbol )
 {
     return boost::get<point_symbolizer>(symbol);
 }
@@ -201,4 +208,3 @@ void export_symbolizer()
              return_value_policy<copy_const_reference>())
         ;
 }
-