diff --git a/eos/file_reader.py b/eos/file_reader.py
index 09cc31e..3f64e81 100644
--- a/eos/file_reader.py
+++ b/eos/file_reader.py
@@ -581,7 +581,7 @@ class AmorEventData(AmorHeader):
                       (_time<=packets.time[-1])]
         beam_monitor = np.recarray(shape=np.shape(_time)[0], dtype=BM_TYPE)
         beam_monitor.time = _time
-        beam_monitor.value[:] =  _signal[:][plse].sum() - _signal[:][base].sum()
+        beam_monitor.value[:] =  np.sum(_signal[:, plse], axis=1) - np.sum(_signal[:, base], axis=1)
         return beam_monitor
 
     def info(self):