diff --git a/src/calibre/library/coloring.py b/src/calibre/library/coloring.py
index 6f98352928..476429549c 100644
--- a/src/calibre/library/coloring.py
+++ b/src/calibre/library/coloring.py
@@ -144,6 +144,10 @@ class Rule(object):  # {{{
             return "cmp(raw_field('%s'), %s, '%s', '%s', '%s')" % (col, val, lt, eq, gt)
 
     def rating_condition(self, col, action, val):
+        if action == 'is set':
+            return "test(field('%s'), '1', '')"%col
+        if action == 'is not set':
+            return "test(field('%s'), '', '1')"%col
         lt, eq, gt = {
                 'eq': ('', '1', ''),
                 'lt': ('1', '', ''),