diff --git a/cmd/mtwebmapper/subbaseline.go b/cmd/mtwebmapper/subbaseline.go
index cd35be0..b218d00 100644
--- a/cmd/mtwebmapper/subbaseline.go
+++ b/cmd/mtwebmapper/subbaseline.go
@@ -61,19 +61,6 @@ func (sb *subBaseLine) ServeHTTP(rw http.ResponseWriter, r *http.Request) {
 			return
 		}
 	}
-	img := common.LoadPNG(baseTile)
-
-	type subImage interface {
-		SubImage(image.Rectangle) image.Image
-	}
-	var si subImage
-	var ok bool
-	if si, ok = img.(subImage); !ok {
-		// Should not happen.
-		http.Error(rw,
-			http.StatusText(http.StatusInternalServerError), http.StatusInternalServerError)
-		return
-	}
 
 	rx := x & ^(^uint(0) << (z - 8))
 	ry := y & ^(^uint(0) << (z - 8))
@@ -83,23 +70,27 @@ func (sb *subBaseLine) ServeHTTP(rw http.ResponseWriter, r *http.Request) {
 	w := uint(256) / parts
 	xo := w * rx
 	yo := w * (parts - 1 - ry)
-	//fmt.Printf("x %d\n", x)
-	//fmt.Printf("y %d\n", y)
-	//fmt.Printf("z %d\n", z)
-	//fmt.Printf("z %d\n", z)
-	//fmt.Printf("parts %d\n", parts)
-	//fmt.Printf("w %d\n", w)
-	//fmt.Printf("xo %d\n", xo)
-	//fmt.Printf("yo %d\n", yo)
-	//fmt.Printf("rx %d\n", rx)
-	//fmt.Printf("ry %d\n", ry)
 
-	img = si.SubImage(image.Rect(int(xo), int(yo), int(xo+w), int(yo+w)))
+	img := common.LoadPNG(baseTile)
+
+	type subImage interface {
+		SubImage(image.Rectangle) image.Image
+	}
+
+	if si, ok := img.(subImage); ok {
+		img = si.SubImage(image.Rect(int(xo), int(yo), int(xo+w), int(yo+w)))
+	} else {
+		// Should not happen.
+		http.Error(rw,
+			http.StatusText(http.StatusInternalServerError), http.StatusInternalServerError)
+	}
+
 	img = blowUp(img)
 
 	rw.Header().Set("Content-Type", "image/png")
 	if etag == "" {
 		if etag, err = createETag(baseTile); err != nil {
+			// Unlikely
 			log.Printf("Cannot create ETag: %s", baseTile)
 		} else {
 			rw.Header().Set("ETag", etag)