diff --git a/gltiles.js b/gltiles.js
index a132658f..0f5e05cf 100644
--- a/gltiles.js
+++ b/gltiles.js
@@ -199,11 +199,11 @@ export default async function makeTileRenderer(gl) {
     }) {
       const layerParams = layerParamsBlock.makeBuffer();
       const transform = layerParams.getVar('transform').asFloatArray();
-      const cellSize = layerParams.getVar('cellSize').asFloatArray();
+      const cellSize = layerParams.getVar('cellSize');
       const stride = layerParams.getVar('stride');
 
       stride.int = width;
-      cellSize[0] = givenCellSize;
+      cellSize.float = givenCellSize;
 
       mat4.fromTranslation(transform, [givenCellSize * left, givenCellSize * top, 0]);
       layerParams.send();
@@ -230,7 +230,7 @@ export default async function makeTileRenderer(gl) {
 
       return {
         get texture() { return texture },
-        get cellSize() { return cellSize[0] },
+        get cellSize() { return cellSize.float },
         get left() { return left },
         get top() { return top },
         get width() { return width },