diff --git a/server/test_mode.py b/server/test_mode.py
index e07560e..c576246 100644
--- a/server/test_mode.py
+++ b/server/test_mode.py
@@ -80,7 +80,7 @@ class TestDataGenerator:
                       throttle, brake, gear, steering):
         buf = bytearray(324)
         struct.pack_into("<i", buf, 0, 1)
-        struct.pack_into("<I", buf, 4, int(time.time() * 1000))
+        struct.pack_into("<I", buf, 4, int(time.time() * 1000) & 0xFFFFFFFF)
         struct.pack_into("<f", buf, 8, max_rpm)
         struct.pack_into("<f", buf, 12, 800.0)
         struct.pack_into("<f", buf, 16, rpm)