diff --git a/eos/file_reader.py b/eos/file_reader.py
index e233128..4a30ad8 100644
--- a/eos/file_reader.py
+++ b/eos/file_reader.py
@@ -568,13 +568,30 @@ class AmorEventData(AmorHeader):
         output += '\n'
         return output
 
+    @staticmethod
+    def concatenate_dropmissing(a1, a2):
+        """
+        Concatenate to recarrays that might have different fields. Drop fields that
+        are not present in either array and give a warning for the missing data.
+        """
+        try:
+            return np.concatenate([a1, a2]).view(np.recarray)
+        except np.exceptions.DTypePromotionError:
+            new_fields = np.dtype([(key, dtype) for key, (dtype, length) in a2.dtype.fields.items() if key in a1.dtype.fields])
+            output = np.recarray(a1.shape[0]+a2.shape[0], dtype=new_fields)
+            for field in new_fields.fields.keys():
+                output[field] = np.concatenate([a1[field], a2[field]])
+            logging.warning("Missing data when combining datasets, "
+                            f"{tuple(a1.dtype.fields.keys())} != {tuple(a2.dtype.fields.keys())}")
+            return output
+
     def append(self, other):
         """
         Append event streams from another file to this one. Adjusts the event indices in the
         packets to stay valid.
         """
         new_events = np.concatenate([self.data.events, other.data.events]).view(np.recarray)
-        new_pulses = np.concatenate([self.data.pulses, other.data.pulses]).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)
         new_packets = np.concatenate([self.data.packets, other.data.packets]).view(np.recarray)