diff --git a/include/mapnik/label_collision_detector.hpp b/include/mapnik/label_collision_detector.hpp
index 7b50c7dc4..1352f8588 100644
--- a/include/mapnik/label_collision_detector.hpp
+++ b/include/mapnik/label_collision_detector.hpp
@@ -133,24 +133,27 @@ namespace mapnik
    };
 
     
-    //quad tree based label collission detector so labels dont appear within a given distance
-    class label_collision_detector4 : boost::noncopyable
-    {
-        struct label
-        {
-            label(Envelope<double> const& b) : box(b) {}
-            label(Envelope<double> const& b, std::wstring const& t) : box(b), text(t) {}
-              
-            Envelope<double> box;
-            std::wstring text;
-        };
-      
-        typedef quad_tree< label > tree_t;
-        tree_t tree_;
+   //quad tree based label collission detector so labels dont appear within a given distance
+   class label_collision_detector4 : boost::noncopyable
+   {
+         struct label
+         {
+               label(Envelope<double> const& b) : box(b) {}
+               label(Envelope<double> const& b, std::wstring const& t) : box(b), text(t) {}
+               
+               Envelope<double> box;
+               std::wstring text;
+         };
+         
+         typedef quad_tree< label > tree_t;
+         Envelope<double> extent_;
+         tree_t tree_;
+         
     public:
 	
         explicit label_collision_detector4(Envelope<double> const& extent)
-            : tree_(extent) {}
+           : extent_(extent),
+             tree_(extent) {}
 	
         bool has_placement(Envelope<double> const& box)
         {
@@ -201,6 +204,10 @@ namespace mapnik
          {
             tree_.clear();
          }
+         Envelope<double> const& extent() const
+         {
+            return extent_;
+         }
     };
 }