diff --git a/cocoa/base/ResultOutline.m b/cocoa/base/ResultOutline.m
index d0d3edb7..f1b691fe 100644
--- a/cocoa/base/ResultOutline.m
+++ b/cocoa/base/ResultOutline.m
@@ -29,13 +29,6 @@ http://www.hardcoded.net/licenses/hs_license
     return (PyResultTree *)py;
 }
 
-/* Override */
-- (void)refresh
-{
-    [super refresh];
-    [outlineView expandItem:nil expandChildren:YES];
-}
-
 /* Public */
 - (BOOL)powerMarkerMode
 {
@@ -128,4 +121,19 @@ http://www.hardcoded.net/licenses/hs_license
         }
     }
 }
+
+/* Python --> Cocoa */
+- (void)refresh /* Override */
+{
+    [super refresh];
+    [outlineView expandItem:nil expandChildren:YES];
+}
+
+- (void)invalidateMarkings
+{
+    for (NSMutableDictionary *props in [itemData objectEnumerator]) {
+        [props removeObjectForKey:@"marked"];
+    }
+    [outlineView setNeedsDisplay:YES];
+}
 @end
\ No newline at end of file
diff --git a/core/app.py b/core/app.py
index 96091492..da1f3319 100644
--- a/core/app.py
+++ b/core/app.py
@@ -243,15 +243,15 @@ class DupeGuru(RegistrableApplication, Broadcaster):
     
     def mark_all(self):
         self.results.mark_all()
-        self.notify('results_changed')
+        self.notify('marking_changed')
     
     def mark_none(self):
         self.results.mark_none()
-        self.notify('results_changed')
+        self.notify('marking_changed')
     
     def mark_invert(self):
         self.results.mark_invert()
-        self.notify('results_changed')
+        self.notify('marking_changed')
     
     def open_selected(self):
         if self.selected_dupes:
@@ -306,7 +306,7 @@ class DupeGuru(RegistrableApplication, Broadcaster):
     def toggle_selected_mark_state(self):
         for dupe in self.selected_dupes:
             self.results.mark_toggle(dupe)
-        self.notify('results_changed')
+        self.notify('marking_changed')
     
     def without_ref(self, dupes):
         return [dupe for dupe in dupes if self.results.get_group_of_duplicate(dupe).ref is not dupe]
diff --git a/core/app_cocoa_inter.py b/core/app_cocoa_inter.py
index ca8227a2..e3abf37a 100644
--- a/core/app_cocoa_inter.py
+++ b/core/app_cocoa_inter.py
@@ -194,6 +194,10 @@ class PyResultOutline(PyOutline):
     def markSelected(self):
         self.py.app.toggle_selected_mark_state()
     
+    # python --> cocoa
+    def invalidate_markings(self):
+        self.cocoa.invalidateMarkings()
+    
 
 class PyStatsLabel(PyGUIObject):
     py_class = StatsLabel
diff --git a/core/gui/base.py b/core/gui/base.py
index 47e28965..0b482519 100644
--- a/core/gui/base.py
+++ b/core/gui/base.py
@@ -21,6 +21,9 @@ class GUIObject(Listener):
     def dupes_selected(self):
         pass
     
+    def marking_changed(self):
+        pass
+    
     def results_changed(self):
         pass
     
diff --git a/core/gui/result_tree.py b/core/gui/result_tree.py
index c778f1ec..afb73e31 100644
--- a/core/gui/result_tree.py
+++ b/core/gui/result_tree.py
@@ -19,8 +19,20 @@ class DupeNode(Node):
         self._app = app
         self._group = group
         self._dupe = dupe
-        self.data = app._get_display_info(dupe, group, False)
-        self.data_delta = app._get_display_info(dupe, group, True)
+        self._data = None
+        self._data_delta = None
+    
+    @property
+    def data(self):
+        if self._data is None:
+            self._data = self._app._get_display_info(self._dupe, self._group, False)
+        return self._data
+    
+    @property
+    def data_delta(self):
+        if self._data_delta is None:
+            self._data_delta = self._app._get_display_info(self._dupe, self._group, True)
+        return self._data_delta
     
     @property
     def markable(self):
@@ -113,6 +125,9 @@ class ResultTree(GUIObject, Tree):
         self.view.refresh()
     
     #--- Event Handlers
+    def marking_changed(self):
+        self.view.invalidate_markings()
+    
     def results_changed(self):
         self._refresh()
         self.view.refresh()
diff --git a/core/gui/stats_label.py b/core/gui/stats_label.py
index 1f7b9ec3..ed1bb232 100644
--- a/core/gui/stats_label.py
+++ b/core/gui/stats_label.py
@@ -21,4 +21,4 @@ class StatsLabel(GUIObject):
     
     def results_changed(self):
         self.view.refresh()
-    
+    marking_changed = results_changed