diff --git a/macrovision.js b/macrovision.js
index d0d1f5c2..1ebf5d57 100644
--- a/macrovision.js
+++ b/macrovision.js
@@ -564,7 +564,7 @@ function drawVerticalScale(ifDirty = false) {
     }
 
     function drawAltitudeLine(ctx, height, label) {
-        const pixelScale = (ctx.canvas.clientHeight - 100) / config.height.toNumber();
+        const pixelScale = (ctx.canvas.clientHeight - 100) / config.height.toNumber("meters");
         const y = ctx.canvas.clientHeight - 50 - (height.toNumber("meters") - config.y) * pixelScale;
         if (y < ctx.canvas.clientHeight - 100) {
             drawTick(ctx, 50, y, label, true);