diff --git a/modules/sachsen/backend.py b/modules/sachsen/backend.py
index 968dda32..4a937313 100644
--- a/modules/sachsen/backend.py
+++ b/modules/sachsen/backend.py
@@ -21,7 +21,7 @@
 from __future__ import with_statement
 
 from .browser import SachsenBrowser
-from weboob.capabilities.gauge import ICapGauge, GaugeSensor, Gauge
+from weboob.capabilities.gauge import ICapGauge, GaugeSensor, Gauge, SensorNotFound
 from weboob.tools.backend import BaseBackend
 
 
@@ -75,9 +75,13 @@ class SachsenLevelBackend(BaseBackend, ICapGauge):
     def iter_gauge_history(self, sensor):
         if not isinstance(sensor, GaugeSensor):
             sensor = self._get_sensor_by_id(sensor)
+        if sensor is None:
+            raise SensorNotFound()
         return self.browser.iter_history(sensor)
 
     def get_last_measure(self, sensor):
         if not isinstance(sensor, GaugeSensor):
             sensor = self._get_sensor_by_id(sensor)
+        if sensor is None:
+            raise SensorNotFound()
         return sensor.lastvalue
diff --git a/weboob/capabilities/gauge.py b/weboob/capabilities/gauge.py
index f33f3de4..8378fd02 100644
--- a/weboob/capabilities/gauge.py
+++ b/weboob/capabilities/gauge.py
@@ -18,10 +18,16 @@
 # along with weboob. If not, see <http://www.gnu.org/licenses/>.
 
 
-from .base import IBaseCap, CapBaseObject, StringField, FloatField, DateField, Field
+from .base import IBaseCap, CapBaseObject, StringField, FloatField, DateField, Field, UserError
 
 
-__all__ = ['Gauge', 'GaugeSensor', 'GaugeMeasure', 'ICapGauge']
+__all__ = ['Gauge', 'GaugeSensor', 'GaugeMeasure', 'ICapGauge', 'SensorNotFound']
+
+
+class SensorNotFound(UserError):
+    """
+    Not found a sensor
+    """
 
 
 class Gauge(CapBaseObject):