diff --git a/src/fix.py b/src/fix.py
index 6a7f46326..7fefebed5 100644
--- a/src/fix.py
+++ b/src/fix.py
@@ -120,6 +120,9 @@ class set(object):
         for x in t:
             self.d[x] = None
 
+    def __len__(self):
+        return len(self.d)
+
     def add(self, x):
         self.d[x] = None