--- bipaddress.py	2015-01-20 20:00:36.325503808 +0100
+++ aipaddress.py	2015-01-20 19:59:57.025308929 +0100
@@ -176,7 +176,9 @@
     it = iter(addresses)
     first = last = next(it)
     for ip in it:
-        if ip._ip != last._ip + 1:
+        if ip._ip == last._ip:
+            continue
+        elif ip._ip != last._ip + 1:
             yield first, last
             first = ip
         last = ip
@@ -347,7 +349,7 @@
             nets.append(ip)
 
     # sort and dedup
-    ips = sorted(set(ips))
+    ips = sorted(ips)
 
     # find consecutive address ranges in the sorted sequence and summarize them
     if ips: