diff --git a/tilerenderer/renderer.go b/tilerenderer/renderer.go
index 98c0e0c..078201a 100644
--- a/tilerenderer/renderer.go
+++ b/tilerenderer/renderer.go
@@ -10,6 +10,7 @@ import (
 	"mapserver/mapblockrenderer"
 	"mapserver/layerconfig"
 	"mapserver/tiledb"
+	"github.com/sirupsen/logrus"
 )
 
 type TileRenderer struct {
@@ -75,6 +76,8 @@ func (tr *TileRenderer) RenderImage(tc coords.TileCoords) (*image.NRGBA, error)
 		return cachedimg.(*image.NRGBA), nil
 	}
 
+	log.WithFields(logrus.Fields{"x": tc.X, "y": tc.Y, "zoom": tc.Zoom}).Debug("RenderImage")
+
 	var layer *layerconfig.Layer
 
 	for _, l := range(tr.layers) {
@@ -131,16 +134,24 @@ func (tr *TileRenderer) RenderImage(tc coords.TileCoords) (*image.NRGBA, error)
 	)
 
 	rect := image.Rect(0, 0, 128, 128)
-	draw.Draw(img, rect, upperLeft, image.ZP, draw.Src)
+	if upperLeft != nil {
+		draw.Draw(img, rect, upperLeft, image.ZP, draw.Src)
+	}
 
 	rect = image.Rect(128, 0, 256, 128)
-	draw.Draw(img, rect, upperRight, image.ZP, draw.Src)
+	if upperRight != nil {
+		draw.Draw(img, rect, upperRight, image.ZP, draw.Src)
+	}
 
 	rect = image.Rect(0, 128, 128, 256)
-	draw.Draw(img, rect, lowerLeft, image.ZP, draw.Src)
+	if lowerLeft != nil {
+		draw.Draw(img, rect, lowerLeft, image.ZP, draw.Src)
+	}
 
 	rect = image.Rect(128, 128, 256, 256)
-	draw.Draw(img, rect, lowerRight, image.ZP, draw.Src)
+	if lowerRight != nil {
+		draw.Draw(img, rect, lowerRight, image.ZP, draw.Src)
+	}
 
 
 	return img, nil
diff --git a/tilerenderer/renderer_test.go b/tilerenderer/renderer_test.go
index 6cfec79..cacdf33 100644
--- a/tilerenderer/renderer_test.go
+++ b/tilerenderer/renderer_test.go
@@ -17,7 +17,7 @@ import (
 )
 
 func TestTileRender(t *testing.T) {
-	logrus.SetLevel(logrus.InfoLevel)
+	logrus.SetLevel(logrus.DebugLevel)
 
 	tmpfile, err := ioutil.TempFile("", "TestTileRender.*.sqlite")
 	if err != nil {
@@ -58,7 +58,7 @@ func TestTileRender(t *testing.T) {
     panic("no renderer")
   }
 
-  coord := coords.NewTileCoords(0,0,12,0)
+  coord := coords.NewTileCoords(0,0,11,0)
 
   data, err := tr.Render(coord)