diff --git a/vendor/clouds3d.js b/vendor/clouds3d.js
index 3952bf0..c779ff5 100644
--- a/vendor/clouds3d.js
+++ b/vendor/clouds3d.js
@@ -405,8 +405,8 @@ function initGroundSystem(glCtx) {
     if (groundCanvas) return; // already initialised
     groundGl = glCtx;
     groundCanvas = document.createElement('canvas');
-    groundCanvas.width = GROUND_TILE_SIZE * GROUND_CORRIDOR_LONG;
-    groundCanvas.height = GROUND_TILE_SIZE * GROUND_CORRIDOR_PERP;
+    groundCanvas.width = GROUND_TILE_SIZE * GROUND_CORRIDOR_PERP;
+    groundCanvas.height = GROUND_TILE_SIZE * GROUND_CORRIDOR_LONG;
     groundCtx = groundCanvas.getContext('2d');
     // Pre-fill with fog colour so partially-loaded mosaic still
     // shows the right base colour