diff --git a/src/hamster/widgets/activityentry.py b/src/hamster/widgets/activityentry.py
index <HASH>..<HASH> 100644
--- a/src/hamster/widgets/activityentry.py
+++ b/src/hamster/widgets/activityentry.py
@@ -149,8 +149,8 @@ class ActivityEntry(gtk.Entry):
 
         #set proper background color (we can do that only on a realised widget)
         bgcolor = self.get_style().bg[gtk.STATE_NORMAL]
-        self.time_icon_cell.set_property("cell-background", bgcolor)
-        self.time_cell.set_property("cell-background", bgcolor)
+        self.time_icon_cell.set_property("cell-background-gdk", bgcolor)
+        self.time_cell.set_property("cell-background-gdk", bgcolor)
 
         text_color = self.get_style().text[gtk.STATE_NORMAL]
         category_color = graphics.Colors.contrast(text_color,  100)
setting cell-background-gdk instead of cell-background property to change the background as the latter seems to be wanting a string. fixes the unreproducible bug <I>. patch by Jamie Strandboge