diff --git a/common/basetilehash.go b/common/basetilehash.go
index 506c464..19e0146 100644
--- a/common/basetilehash.go
+++ b/common/basetilehash.go
@@ -10,32 +10,27 @@ import (
 	"sync"
 )
 
-type btPos struct {
-	x int
-	y int
-}
-
 type BaseTileHash struct {
 	// XXX: Maybe use some kind of LRU cache instead?
-	hashes map[btPos][]byte
+	hashes map[struct{ x, y int }][]byte
 	sync.Mutex
 }
 
 func NewBaseTileHash() *BaseTileHash {
-	return &BaseTileHash{hashes: map[btPos][]byte{}}
+	return &BaseTileHash{hashes: map[struct{ x, y int }][]byte{}}
 }
 
 func (bth *BaseTileHash) Update(x, y int, img image.Image) bool {
 	hash := SHA1Image(img)
-	key := btPos{x, y}
+	key := struct{ x, y int }{x, y}
 	bth.Lock()
 	defer bth.Unlock()
 	if old, found := bth.hashes[key]; found {
-		equals := bytes.Equal(old, hash)
-		if !equals {
+		if !bytes.Equal(old, hash) {
 			bth.hashes[key] = hash
+			return true
 		}
-		return !equals
+		return false
 	}
 	bth.hashes[key] = hash
 	return true