--- a/Set.st	Wed May 18 10:42:16 2016 +0200
+++ b/Set.st	Wed May 18 10:42:54 2016 +0200
@@ -1301,6 +1301,7 @@
     "return the number of occurrences of anObject in the receiver.
      As I am a Set, this can only return 0 or 1."
 
+    tally == 0 ifTrue:[^ 0]. 
     (self find:(anObject ? NilEntry) ifAbsent:0) == 0 ifTrue:[^ 0].
     ^ 1