diff --git a/homeassistant/components/nzbget/sensor.py b/homeassistant/components/nzbget/sensor.py
index 5bfde7e7c2b..9f94d458f42 100644
--- a/homeassistant/components/nzbget/sensor.py
+++ b/homeassistant/components/nzbget/sensor.py
@@ -127,6 +127,6 @@ class NZBGetSensor(NZBGetEntity, SensorEntity):
 
         if "UpTimeSec" in sensor_type and value > 0:
             uptime = utcnow() - timedelta(seconds=value)
-            return uptime.replace(microsecond=0).isoformat()
+            return uptime.replace(microsecond=0)
 
         return value