diff --git a/docs/HISTORY.txt b/docs/HISTORY.txt
index 8e3fd52..4dabcc1 100644
--- a/docs/HISTORY.txt
+++ b/docs/HISTORY.txt
@@ -15,6 +15,9 @@ Changelog
 
 * Do not exclude content types which are not allowed in navigation [ebrehault]
 
+* Ignore missing values, content objects can go away or the content of a source may change.
+  [gaudenz]
+
 1.0.6 (2012-09-28)
 ------------------
 
diff --git a/plone/formwidget/contenttree/widget.py b/plone/formwidget/contenttree/widget.py
index 9b9d64b..00b6694 100644
--- a/plone/formwidget/contenttree/widget.py
+++ b/plone/formwidget/contenttree/widget.py
@@ -121,6 +121,7 @@ class ContentTreeBase(Explicit):
     hidden_template = ViewPageTemplateFile('hidden.pt')
     display_template = None  # set by subclass
     recurse_template = ViewPageTemplateFile('input_recurse.pt')
+    ignoreMissing = True
 
     # Parameters passed to the JavaScript function
     folderEvent = 'click'