diff --git a/libeos/file_reader.py b/libeos/file_reader.py
index 8217533..7a61e5f 100644
--- a/libeos/file_reader.py
+++ b/libeos/file_reader.py
@@ -228,7 +228,7 @@ class AmorData:
     def associate_pulse_with_current(self):
         if self.monitorType == 'protonCharge':
             self.currentTime -= self.seriesStartTime
-            currentInterpolator = sp.interpolate.interp1d(self.currentTime, self.current, kind='previous', bounds_error=False, fill_value='extrapolate')
+            currentInterpolator = sp.interpolate.interp1d(self.currentTime, self.current, kind='previous', bounds_error=False, fill_value=0)
             charge = np.array(currentInterpolator(self.pulseTimeS) * 2*self.tau *1e-3, dtype=float)
             # filter low-current pulses
             charge = np.where(charge > 2*self.tau * 1e-1, charge, 0)
@@ -242,7 +242,7 @@ class AmorData:
         if self.monitorType == 'protonCharge':
             # associate each pulse with a proton current
             self.currentTime -= self.seriesStartTime
-            currentInterpolator = sp.interpolate.interp1d(self.currentTime, self.current, kind='previous', bounds_error=False, fill_value='extrapolate')
+            currentInterpolator = sp.interpolate.interp1d(self.currentTime, self.current, kind='previous', bounds_error=False, fill_value=0)
             charge = np.array(currentInterpolator(self.pulseTimeS) * 2*self.tau *1e-3, dtype=float)
             # TODO: activate the following filter AND remove the respective events :
             # remove events (wallTime, tof and pixelID) from stream for pulses with too low monitor signal