diff --git a/yolox/tracker/basetrack.py b/yolox/tracker/basetrack.py
index d5837b05..8b53fb97 100644
--- a/yolox/tracker/basetrack.py
+++ b/yolox/tracker/basetrack.py
@@ -10,9 +10,9 @@ class TrackState(object):
 
 
 class BaseTrack(object):
-    def __init__(self):
-        self._count = 0
+    _count = 0
 
+    def __init__(self):
         self.track_id = 0
         self.is_activated = False
         self.state = TrackState.New
@@ -32,9 +32,10 @@ def __init__(self):
     def end_frame(self):
         return self.frame_id
 
-    def next_id(self):
-        self._count += 1
-        return self._count
+    @staticmethod
+    def next_id():
+        BaseTrack._count += 1
+        return BaseTrack._count
 
     def activate(self, *args):
         raise NotImplementedError
diff --git a/yolox/tracker/byte_tracker.py b/yolox/tracker/byte_tracker.py
index 2d004599..a0ee3cf8 100644
--- a/yolox/tracker/byte_tracker.py
+++ b/yolox/tracker/byte_tracker.py
@@ -7,13 +7,13 @@
 import torch.nn.functional as F
 
 from .kalman_filter import KalmanFilter
-from yolox.tracker import matching
+from . import matching
 from .basetrack import BaseTrack, TrackState
 
 class STrack(BaseTrack):
     shared_kalman = KalmanFilter()
     def __init__(self, tlwh, score):
-
+        super().__init__()
         # wait activate
         self._tlwh = np.asarray(tlwh, dtype=np.float)
         self.kalman_filter = None
diff --git a/yolox/tracker/matching.py b/yolox/tracker/matching.py
index d36a6cf5..3fce605a 100644
--- a/yolox/tracker/matching.py
+++ b/yolox/tracker/matching.py
@@ -5,7 +5,7 @@
 from scipy.spatial.distance import cdist
 
 from cython_bbox import bbox_overlaps as bbox_ious
-from yolox.tracker import kalman_filter
+from . import kalman_filter
 import time
 
 def merge_matches(m1, m2, shape):