diff --git a/utils/he_ipv6/tunnel.py b/utils/he_ipv6/tunnel.py
index 014ae97..7487d83 100644
--- a/utils/he_ipv6/tunnel.py
+++ b/utils/he_ipv6/tunnel.py
@@ -128,7 +128,7 @@ class Assignment(object):
     def parse_alloc(self):
         self.alloc_block = self.alloc.ip.alloc_block
         self.iface_blocks = self.alloc_block.extract_subnet(self.prefix, count = 1)
-        logger.debug('Allocation blocks for {0}: {1}'.format(self.iface, ','.join(self.iface_blocks)))
+        logger.debug('Allocation blocks for {0}: {1}'.format(self.iface, ','.join([str(i) for i in self.iface_blocks])))
         for i in self.iface_blocks:
             # DHCPv6 range.
             _base = str(i.ip).rstrip(':')