diff --git a/steer-pid.py b/steer-pid.py
index bcc51a7..f6130aa 100644
--- a/steer-pid.py
+++ b/steer-pid.py
@@ -87,7 +87,7 @@ for chunk in stream.iter_content(chunk_size=1024):
                 #     motorR.stop()
                 else:
                     tnow = datetime.now()
-                    dtmicro = tprev - tnow
+                    dtmicro = tnow - tprev
                     dtms = dtmicro.seconds * 1000 + dtmicro.microseconds // 1000
                     tprev = tnow