diff --git a/src/gui/views/treemodels/flatbasemodel.py b/src/gui/views/treemodels/flatbasemodel.py
index 005a294b4..8a1f40a5f 100644
--- a/src/gui/views/treemodels/flatbasemodel.py
+++ b/src/gui/views/treemodels/flatbasemodel.py
@@ -303,6 +303,9 @@ class FlatNodeMap(object):
         :Returns: path of the row inserted in the treeview
         :Returns type: integer or None
         """
+        if srtkey_hndl[1] in self._hndl2index:
+            raise ValueError, 'Attempt to add row twice to the model (%s)' % \
+                                srtkey_hndl[1]
         if not self._identical:
             bisect.insort_left(self._fullhndl, srtkey_hndl)
             if allkeyonly:
diff --git a/src/gui/views/treemodels/treebasemodel.py b/src/gui/views/treemodels/treebasemodel.py
index c077cb1e3..bb3377c3c 100644
--- a/src/gui/views/treemodels/treebasemodel.py
+++ b/src/gui/views/treemodels/treebasemodel.py
@@ -590,8 +590,8 @@ class TreeBaseModel(gtk.GenericTreeModel):
         Otherwise, a node should never be added twice!
         """
         if not self.group_can_have_handle:
-            raise ValueError, 'attempt to add twice a node to the model %s' % \
-                                str(parent) + ' ' + str(child) + ' ' + sortkey
+            raise ValueError, 'Attempt to add node twice to the model (%s:%s)' \
+                                % (str(parent), str(child))
         if handle:
             node.set_handle(handle)
             if not self._in_build: