diff --git a/recipes/Python/576816_Interval/recipe-576816.py b/recipes/Python/576816_Interval/recipe-576816.py
index 11fe0ca22..08258d34d 100644
--- a/recipes/Python/576816_Interval/recipe-576816.py
+++ b/recipes/Python/576816_Interval/recipe-576816.py
@@ -84,7 +84,8 @@ def subset(self, other):
 
     def proper_subset(self, other):
         "@return: True iff self is proper subset of other."
-        return self.start > other.start and self.end < other.end
+        return ((self.start > other.start and self.end <= other.end) or
+                (self.start >= other.start and self.end < other.end))
          
 
     def empty(self):