diff --git a/croppa/main.py b/croppa/main.py
index 6de9345..9271fc5 100644
--- a/croppa/main.py
+++ b/croppa/main.py
@@ -230,7 +230,13 @@ class MotionTracker:
         
     def from_dict(self, data: Dict):
         """Load from dictionary for deserialization"""
-        self.tracking_points = data.get('tracking_points', {})
+        # Convert string keys back to integers for tracking_points
+        tracking_points_data = data.get('tracking_points', {})
+        self.tracking_points = {}
+        for frame_str, points in tracking_points_data.items():
+            frame_num = int(frame_str)  # Convert string key to integer
+            self.tracking_points[frame_num] = points
+        
         self.tracking_enabled = data.get('tracking_enabled', False)
         self.base_crop_rect = data.get('base_crop_rect', None)
         self.base_zoom_center = data.get('base_zoom_center', None)