diff --git a/squinnondation/hazel.py b/squinnondation/hazel.py
index 2a4a5ab..4a1da53 100644
--- a/squinnondation/hazel.py
+++ b/squinnondation/hazel.py
@@ -36,8 +36,8 @@ class Hazelnut:
             # See https://fr.wikipedia.org/wiki/Adresse_IPv6_mappant_IPv4
             address = "::ffff:" + socket.getaddrinfo(address, None, socket.AF_INET)[0][4][0]
 
-        self.addresses = list()
-        self.addresses.append((address, port))
+        self.addresses = set()
+        self.addresses.add((address, port))
 
     @property
     def potential(self) -> bool:
@@ -53,7 +53,7 @@ class Hazelnut:
         A client can have multiple addresses.
         We contact it only on one of them.
         """
-        return self.addresses[0]
+        return list(self.addresses)[0]
 
     @property
     def banned(self) -> bool:
@@ -68,6 +68,19 @@ class Hazelnut:
     def __str__(self):
         return repr(self)
 
+    def merge(self, other: "Hazelnut") -> "Hazelnut":
+        """
+        Merge the hazelnut data with one other.
+        The symmetric and active properties are kept from the original client.
+        """
+        self.errors = max(self.errors, other.errors)
+        self.last_hello_time = max(self.last_hello_time, other.last_hello_time)
+        self.last_long_hello_time = max(self.last_hello_time, other.last_long_hello_time)
+        self.addresses.update(self.addresses)
+        self.addresses.update(other.addresses)
+        self.id = self.id if self.id > 0 else other.id
+        return self
+
 
 class Squirrel(Hazelnut):
     """
@@ -686,19 +699,13 @@ class Squirrel(Hazelnut):
             if addr in self.hazelnuts:
                 # Merge with the previous hazel
                 old_hazel = self.hazelnuts[addr]
-                for other_addr in old_hazel.addresses:
-                    if other_addr not in hazelnut.addresses:
-                        hazelnut.addresses.append(other_addr)
-                    self.hazelnuts[other_addr] = hazelnut
+                hazelnut.merge(old_hazel)
             self.hazelnuts[addr] = hazelnut
 
         for other_hazel in list(self.hazelnuts.values()):
             if other_hazel.id == hazelnut.id > 0 and other_hazel != hazelnut:
                 # The hazelnut with the same id is known as a different address. We merge everything
-                for addr in other_hazel.addresses:
-                    self.hazelnuts[addr] = hazelnut
-                    if addr not in hazelnut.addresses:
-                        hazelnut.addresses.append(addr)
+                hazelnut.merge(other_hazel)
 
     def send_neighbours(self) -> None:
         """