diff --git a/src/js/game/hud/parts/building_placer.js b/src/js/game/hud/parts/building_placer.js
index 7dccb7a4..7d618b6b 100644
--- a/src/js/game/hud/parts/building_placer.js
+++ b/src/js/game/hud/parts/building_placer.js
@@ -216,8 +216,8 @@ export class HUDBuildingPlacer extends HUDBuildingPlacerLogic {
             const dimensions = metaBuilding.getDimensions(variant);
             const sprite = metaBuilding.getPreviewSprite(0, variant);
             const spriteWrapper = makeDiv(element, null, ["iconWrap"]);
-            spriteWrapper.setAttribute("data-tile-w", dimensions.x);
-            spriteWrapper.setAttribute("data-tile-h", dimensions.y);
+            spriteWrapper.setAttribute("data-tile-w", String(dimensions.x));
+            spriteWrapper.setAttribute("data-tile-h", String(dimensions.y));
 
             spriteWrapper.innerHTML = sprite.getAsHTML(iconSize * dimensions.x, iconSize * dimensions.y);