diff --git a/src/orisys/tracker.py b/src/orisys/tracker.py
index 0e67140..c30c28a 100644
--- a/src/orisys/tracker.py
+++ b/src/orisys/tracker.py
@@ -59,6 +59,8 @@ class Tracker:
         if self.cuda:
             return self.track_cuda(frame)
         else:
+            if frame.ndim == 3:
+                frame = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
             return self.track_cpu(frame)
     
     def track_cuda(self, frame):