diff --git a/examples/traffic_analysis/inference_example.py b/examples/traffic_analysis/inference_example.py
index 787db52b..baa98c00 100644
--- a/examples/traffic_analysis/inference_example.py
+++ b/examples/traffic_analysis/inference_example.py
@@ -51,7 +51,8 @@ class DetectionsManager:
         if len(detections_all) > 0:
             detections_all.class_id = np.vectorize(
                 lambda x: self.tracker_id_to_zone_id.get(x, -1)
-            )(detections_all.tracker_id)
+            )
+            (detections_all.tracker_id)
         else:
             detections_all.class_id = np.array([], dtype=int)
         return detections_all[detections_all.class_id != -1]