diff --git a/cmd/mtwebmapper/subbaseline.go b/cmd/mtwebmapper/subbaseline.go
index b714569..a9b2c35 100644
--- a/cmd/mtwebmapper/subbaseline.go
+++ b/cmd/mtwebmapper/subbaseline.go
@@ -41,7 +41,7 @@ func (sb *subBaseLine) ServeHTTP(rw http.ResponseWriter, r *http.Request) {
 		http.ServeFile(rw, r, filepath.Join(sb.mapDir,
 			strconv.Itoa(int(z)),
 			strconv.Itoa(int(x)),
-			fmt.Sprintf("%d.png", y)))
+			strconv.Itoa(int(y))+".png"))
 		return
 	}
 
@@ -52,7 +52,10 @@ func (sb *subBaseLine) ServeHTTP(rw http.ResponseWriter, r *http.Request) {
 	ty := y >> (z - 8)
 
 	baseTile := filepath.Join(
-		sb.mapDir, "8", strconv.Itoa(int(tx)), fmt.Sprintf("%d.png", ty))
+		sb.mapDir,
+		"8",
+		strconv.Itoa(int(tx)),
+		strconv.Itoa(int(ty))+".png")
 
 	var err error
 	var fi os.FileInfo
@@ -61,11 +64,7 @@ func (sb *subBaseLine) ServeHTTP(rw http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	if checkLastModified(rw, r, fi.ModTime()) {
-		return
-	}
-
-	if checkETag(rw, r, fi) {
+	if checkLastModified(rw, r, fi.ModTime()) || checkETag(rw, r, fi) {
 		return
 	}
 
@@ -99,7 +98,6 @@ func (sb *subBaseLine) ServeHTTP(rw http.ResponseWriter, r *http.Request) {
 	rw.Header().Set("Content-Type", "image/png")
 	if err = png.Encode(rw, img); err != nil {
 		log.Printf("WARN: encoding image failed: %s", err)
-		return
 	}
 }
 
diff --git a/cmd/mtwebmapper/tilesupdater.go b/cmd/mtwebmapper/tilesupdater.go
index cadd3ff..54100ac 100644
--- a/cmd/mtwebmapper/tilesupdater.go
+++ b/cmd/mtwebmapper/tilesupdater.go
@@ -255,7 +255,7 @@ func updatePyramidTile(scratch *image.RGBA, level int, baseDir string, j xzm) er
 				baseDir,
 				strconv.Itoa(level+1),
 				strconv.Itoa(bx+o[0]),
-				fmt.Sprintf("%d.png", bz+o[1]))
+				strconv.Itoa(bz+o[1])+".png")
 			img := common.LoadPNG(path)
 			img = resize.Resize(128, 128, img, resize.Lanczos3)
 			sr := img.Bounds()