diff --git a/include/mapnik/hextree.hpp b/include/mapnik/hextree.hpp
index 042c6b9df..9703e8eb9 100644
--- a/include/mapnik/hextree.hpp
+++ b/include/mapnik/hextree.hpp
@@ -263,8 +263,10 @@ public:
     {
 	byte a = preprocessAlpha(c.a);
 	unsigned ind=0;
-	if (a < InsertPolicy::MIN_ALPHA || colors_ <= 1)
+	if (a < InsertPolicy::MIN_ALPHA || colors_ == 0)
 	    return 0;
+        if (colors_ == 1)
+            return pal_remap_[has_hole_?1:0];
 
 	rgba_hash_table::iterator it = color_hashmap_.find(c);
 	if (it == color_hashmap_.end())
@@ -472,7 +474,7 @@ private:
 	    }
 	    tries=0;
 	    // ignore leaves and also nodes with small mean error and not excessive number of pixels
-	    if (cur_node->reduce_cost / cur_node->pixel_count * std::log(long(cur_node->pixel_count)) > 20
+	    if ((cur_node->reduce_cost / cur_node->pixel_count + 1) * std::log(long(cur_node->pixel_count)) > 15
 		&& cur_node->children_count > 0)
 	    {
 		colors_--;