diff --git a/EMT/lmtanalysis/BuildEventWaterPoint.py b/EMT/lmtanalysis/BuildEventWaterPoint.py
index b9bcefab8bccb4e2656ce71551120536ee7522df..b97d3ed0c7b9fb5bc936432a5ba8a438a5342270 100644
--- a/EMT/lmtanalysis/BuildEventWaterPoint.py
+++ b/EMT/lmtanalysis/BuildEventWaterPoint.py
@@ -95,7 +95,7 @@ def reBuildEvent(connection, file, tmin=None, tmax=None, pool = None, animalType
             mass_z = []
             for t in range(event.startFrame, event.endFrame + 1):
                 mass_z.append(dicA[t].massZ)
-            if mean(mass_z) < parameters.MINIMUM_MASS_Z:
+            if np.mean(mass_z) < parameters.MINIMUM_MASS_Z:
                 waterStopTimeLine.removeEventAt(event.startFrame)
 
         waterStopTimeLine.endRebuildEventTimeLine(connection)