diff --git a/QtPyLoT.py b/QtPyLoT.py
index dacfa693..e429307e 100755
--- a/QtPyLoT.py
+++ b/QtPyLoT.py
@@ -675,7 +675,24 @@ class MainWindow(QMainWindow):
         if not event:
             event = self.get_current_event()
         data = Data(self, event)
-        data += Data(self, evtdata=fname)
+        try:
+            data_new = Data(self, evtdata=fname)
+            data += data_new
+        except ValueError:
+            qmb = QMessageBox(self, icon=QMessageBox.Question,
+                              text='Warning: Missmatch in event identifiers {} and {}. Continue?'.format(
+                                  data_new.get_evt_data().resource_id,
+                                  data.get_evt_data().resource_id),
+                              windowTitle='PyLoT - Load data warning')
+            qmb.setStandardButtons(QMessageBox.Yes | QMessageBox.No)
+            qmb.setDefaultButton(QMessageBox.No)
+            ret = qmb.exec_()
+            if ret == qmb.Yes:
+                data_new.setNew()
+                data += data_new
+            else:
+                return
+
         self.data = data
         print('Loading {} picks from file {}.'.format(type, fname))
         if not loc:
diff --git a/pylot/core/io/data.py b/pylot/core/io/data.py
index 2efcb4c9..47e74053 100644
--- a/pylot/core/io/data.py
+++ b/pylot/core/io/data.py
@@ -74,6 +74,8 @@ class Data(object):
 
     def __add__(self, other):
         assert isinstance(other, Data), "operands must be of same type 'Data'"
+        rs_id = self.get_evt_data().get('resource_id')
+        rs_id_other = other.get_evt_data().get('resource_id')        
         if other.isNew() and not self.isNew():
             picks_to_add = other.get_evt_data().picks
             old_picks = self.get_evt_data().picks
@@ -85,7 +87,7 @@ class Data(object):
             self.evtdata = new.get_evt_data()
         elif self.isNew() and other.isNew():
             pass
-        elif self.get_evt_data().get('id') == other.get_evt_data().get('id'):
+        elif rs_id == rs_id_other:
             other.setNew()
             return self + other
         else:
@@ -354,10 +356,16 @@ class Data(object):
                 self.setEvtData(event)
             else:
                 # prevent overwriting original pick information
-                picks =  copy.deepcopy(self.get_evt_data().picks)
+                event_old = self.get_evt_data()
+                print(event_old.resource_id, event.resource_id)
+                if not event_old.resource_id == event.resource_id:
+                    print("WARNING: Missmatch in event resource id's: {} and {}".format(
+                        event_old.resource_id,
+                        event.resource_id))
+                picks = copy.deepcopy(event_old.picks)
                 event = merge_picks(event, picks)
                 # apply event information from location
-                self.get_evt_data().update(event)
+                event_old.update(event)
 
         applydata = {'pick': applyPicks,
                      'event': applyEvent}
diff --git a/pylot/core/util/event.py b/pylot/core/util/event.py
index 48667a07..1db5fac7 100644
--- a/pylot/core/util/event.py
+++ b/pylot/core/util/event.py
@@ -15,8 +15,9 @@ class Event(ObsPyEvent):
     Pickable class derived from ~obspy.core.event.Event containing information on a single event.
     '''
     def __init__(self, path):
+        self.pylot_id = path.split('/')[-1]
         # initialize super class
-        super(Event, self).__init__(resource_id=ResourceIdentifier(path.split('/')[-1]))
+        super(Event, self).__init__(resource_id=ResourceIdentifier('smi:local/'+self.pylot_id))
         self.path = path
         self.database = path.split('/')[-2]
         self.datapath = path.split('/')[-3]