diff --git a/gossipy/core.py b/gossipy/core.py
index a10f271..c6206f5 100644
--- a/gossipy/core.py
+++ b/gossipy/core.py
@@ -339,8 +339,8 @@ def __init__(self, num_nodes: int, topology: Optional[Union[np.ndarray, csr_matr
                 for node in range(num_nodes):
                     self._topology[node] = list(topology.getrow(node).nonzero()[-1])
         else:
-            #self._topology = {i: None for i in range(num_nodes)}
-            self._topology = defaultdict(lambda: range(num_nodes))
+            self._topology = {i: [j for j in range(num_nodes) if j != i] for i in range(num_nodes)}
+            # self._topology = defaultdict(lambda: range(num_nodes))
 
     # docstr-coverage:inherited
     def size(self, node: Optional[int]=None) -> int:
diff --git a/gossipy/node.py b/gossipy/node.py
index 4eb047a..8a22174 100644
--- a/gossipy/node.py
+++ b/gossipy/node.py
@@ -103,6 +103,9 @@ def get_peer(self) -> int:
         """
 
         peers = self.p2p_net.get_peers(self.idx)
+        if not peers:
+            LOG.warning("Node %d has no peers.", self.idx)
+            return None
         return random.choice(peers) if peers else choice_not_n(0, self.p2p_net.size(), self.idx)
         
     def timed_out(self, t: int) -> bool:
@@ -737,6 +740,8 @@ def timed_out(self, t: int) -> int:
     def get_peer(self) -> int:
         if self.step == 1 or not self.best_nodes:
             peer = super().get_peer()
+            if peer is None:
+                return None
             if self.step == 1:
                 self.selected[peer] += 1
             return peer
diff --git a/gossipy/simul.py b/gossipy/simul.py
index fcb2a98..a9b87ba 100644
--- a/gossipy/simul.py
+++ b/gossipy/simul.py
@@ -395,6 +395,8 @@ def start(self, n_rounds: int=100) -> None:
                     if node.timed_out(t):
 
                         peer = node.get_peer()
+                        if peer is None:
+                            break
                         msg = node.send(t, peer, self.protocol)
                         self.notify_message(False, msg)
                         if msg:
@@ -599,6 +601,8 @@ def start(self, n_rounds: int=100) -> Tuple[List[float], List[float]]:
                     if node.timed_out(t):
                         if random() < self.accounts[i].proactive():
                             peer = node.get_peer()
+                            if peer is None:
+                                break
                             msg = node.send(t, peer, self.protocol)
                             self.notify_message(False, msg)
                             if msg: 
@@ -632,6 +636,8 @@ def start(self, n_rounds: int=100) -> Tuple[List[float], List[float]]:
                                 self.accounts[msg.receiver].sub(reaction)
                                 for _ in range(reaction):
                                     peer = node.get_peer()
+                                    if peer is None:
+                                        break
                                     msg = node.send(t, peer, self.protocol)
                                     self.notify_message(False, msg)
                                     if msg: