diff --git a/system/selections.py b/system/selections.py
index b52b930..5127112 100644
--- a/system/selections.py
+++ b/system/selections.py
@@ -28,6 +28,7 @@ class SelectionTree(gtk.TreeView):
         self._selections = {}
 
         self.set_headers_visible(True)
+        self._current_dim = None
 
     def set_identifier_list(self, identifier_list):
         self._identifier_list = identifier_list
@@ -40,6 +41,7 @@ class SelectionTree(gtk.TreeView):
         
     def selection_changed(self, selection):
         self.update_dims(selection.keys())
+        self._update_current_dim()
         
     def dataset_changed(self):
         self.selection_changed(self.project.get_selection())
@@ -54,10 +56,14 @@ class SelectionTree(gtk.TreeView):
     def on_row_activated(self, treeview, path, column):
         i = self.store.get_iter(path)
         p = self.store.iter_parent(i)
-        dim = self.store.get_value(p, 0)
-        id_list = self.project.get_selection()[dim]
-        self._identifier_list.set_identifiers(id_list)
+        self._current_dim = self.store.get_value(p, 0)
+        self._update_current_dim()
         
+    def _update_current_dim(self):
+        if not self._current_dim:
+            return
+        id_list = self.project.get_selection()[self._current_dim]
+        self._identifier_list.set_identifiers(id_list)
 
 class IdentifierList(gtk.TreeView):