diff --git a/Dockerfile b/Dockerfile
index 67d17bb..bde770e 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -38,5 +38,6 @@ COPY --from=backend /output /backend/psn.so
 COPY backend/psn_server.py /backend/psn_server.py
 COPY --from=frontend /frontend/dist /backend/static
 
+WORKDIR /backend
 
 ENTRYPOINT ["python3", "/backend/psn_server.py"]
diff --git a/backend/psn_server.py b/backend/psn_server.py
index f848850..a492e99 100644
--- a/backend/psn_server.py
+++ b/backend/psn_server.py
@@ -22,7 +22,7 @@ class TrackerData:
 trackers = {}
 
 
-for i in NUM_TRACKERS:
+for i in range(NUM_TRACKERS):
     trackers[i] = psn.Tracker(i, f"Tracker {i}")
     trackers[i].set_pos(psn.Float3(0, 0, 0))