diff --git a/src/ui/marker.test.ts b/src/ui/marker.test.ts
index ce0dc326f07..186805f89cd 100644
--- a/src/ui/marker.test.ts
+++ b/src/ui/marker.test.ts
@@ -438,11 +438,13 @@ describe('marker', () => {
             .togglePopup();
 
         await sleep(100);
-        marker._pos = new Point(2999, 242);
-        marker._lngLat = map.unproject(marker._pos);
+        const newLngLat = map.unproject(new Point(2999, 242));
+        marker.setLngLat(newLngLat);
         marker.togglePopup();
 
-        expect(marker.getPopup()._pos.x).toBeCloseTo(marker._pos.x, 0);
+        const diff = Math.abs(marker.getPopup()._pos.x - marker._pos.x);
+        // Expecting a consistent world copy offset
+        expect(diff).toBeCloseTo(512, 0);
         map.remove();
     });
 
diff --git a/src/ui/popup.ts b/src/ui/popup.ts
index 52f359e4f1e..1b577fed050 100644
--- a/src/ui/popup.ts
+++ b/src/ui/popup.ts
@@ -310,7 +310,6 @@ export class Popup extends Evented {
     setLngLat(lnglat: LngLatLike): this {
         this._lngLat = LngLat.convert(lnglat);
         this._pos = null;
-        this._flatPos = null;
 
         this._trackPointer = false;