diff --git a/eos/file_reader.py b/eos/file_reader.py
index 998222b..9a7abc9 100644
--- a/eos/file_reader.py
+++ b/eos/file_reader.py
@@ -553,6 +553,8 @@ class AmorEventData(AmorHeader):
         return proton_current
 
     def read_beam_monitor_stream(self, packets):
+        if self._beam_monitor is None:
+            return None
         _signal = self._beam_monitor.signal
         _time = self._beam_monitor.time
         plse = np.array([0, 5, 6, 11])
@@ -599,7 +601,10 @@ class AmorEventData(AmorHeader):
         new_events = np.concatenate([self.data.events, other.data.events]).view(np.recarray)
         new_pulses = self.concatenate_dropmissing(self.data.pulses, other.data.pulses)
         new_proton_current = np.concatenate([self.data.proton_current, other.data.proton_current]).view(np.recarray)
-        new_beam_monitor = np.concatenate([self.data.beam_monitor, other.data.beam_monitor]).view(np.recarray)
+        if self.data.beam_monitor is None or other.data.beam_monitor is None:
+            new_beam_monitor = None
+        else:
+            new_beam_monitor = np.concatenate([self.data.beam_monitor, other.data.beam_monitor]).view(np.recarray)
         new_packets = np.concatenate([self.data.packets, other.data.packets]).view(np.recarray)
         new_packets.start_index[self.data.packets.shape[0]:] += self.data.events.shape[0]
         self.data = AmorEventStream(new_events, new_packets, new_pulses, new_proton_current, new_beam_monitor)