diff --git a/index.js b/index.js
index 39a1993..707c9e2 100644
--- a/index.js
+++ b/index.js
@@ -75,7 +75,7 @@ abaculus.tileList = function(z, s, center, tileSize) {
         h = center.h;
     var dimensions = {x: w, y: h};
     var size = tileSize || 256;
-    var ts = Math.round(size * s);
+    var ts = Math.floor(size * s);
 
     var centerCoordinate = {
         column: x / size,