diff --git a/tilemapper/renderer.go b/tilemapper/renderer.go
index 9c2d6f5..f79e522 100644
--- a/tilemapper/renderer.go
+++ b/tilemapper/renderer.go
@@ -50,7 +50,8 @@ func NewRenderer(xOfs, zOfs int16, width, height int) (renderer *Renderer) {
 		xOfs:    xOfs,
 		zOfs:    zOfs,
 		yBuffer: yBuffer,
-		cBuffer: cBuffer}
+		cBuffer: cBuffer,
+		yMin:    yMin}
 	return
 }
 
@@ -65,11 +66,9 @@ func (r *Renderer) RenderBlock(block *common.Block, nameIndex map[string]int32)
 
 	// We do not need to render the block if the whole 16x16 area
 	// is already filled and the block is strictly below.
-	w := r.width << 4
-	ofs := int(bz)*w<<4 + int(bx)<<4
-
 	blockY := int32(block.Coord.Y) << 4
 	pos := int(bz)*r.width + int(bx)
+	//fmt.Printf("pos: %d %d\n", pos, len(r.yMin))
 	if blockY < r.yMin[pos] {
 		r.Rejected++
 		return
@@ -81,6 +80,9 @@ func (r *Renderer) RenderBlock(block *common.Block, nameIndex map[string]int32)
 		return
 	}
 
+	w := r.width << 4
+	ofs := int(bz)*w<<4 + int(bx)<<4
+
 	yMin := int32(math.MaxInt32)
 	for z := 0; z < 16; z++ {
 		for x := 0; x < 16; x++ {