diff --git a/lib/drag.js b/lib/drag.js
index afffd72..ca57b45 100644
--- a/lib/drag.js
+++ b/lib/drag.js
@@ -76,6 +76,7 @@ export class DragManager {
 
         if (hoveredSlot !== -1 && hoveredSlot !== originalSlot) {
             const matrix = layout.escalator.getLayoutForCount(tracker.size);
+            if (!matrix || hoveredSlot >= matrix.size || originalSlot >= matrix.size) return;
             const targetRect = matrix.getEstate(hoveredSlot).toAbsolute(monitorRect, gaps);
             
             indicator.set_position(targetRect.x, targetRect.y);
@@ -120,6 +121,7 @@ export class DragManager {
     }
 
     _restoreWindowGeometry(tracker, matrix, slotToFind, targetEstateSlot, monitorRect, gaps) {
+        if (!matrix || targetEstateSlot >= matrix.size) return;
         const win = tracker.windows.find(w => tracker.getSlot(w) === slotToFind);
         if (!win) return;
         const wrap = this.controller._windowWrappers.get(win);