diff --git a/electrum/address_synchronizer.py b/electrum/address_synchronizer.py
index cea1ed0f3..3e490f8f4 100644
--- a/electrum/address_synchronizer.py
+++ b/electrum/address_synchronizer.py
@@ -182,6 +182,7 @@ class AddressSynchronizer(Logger, EventListener):
                 self.add_unverified_or_unconfirmed_tx(tx_hash, tx_height)
 
     def start_network(self, network: Optional['Network']) -> None:
+        assert self.network is None, "already started"
         self.network = network
         if self.network is not None:
             self.synchronizer = Synchronizer(self)
diff --git a/electrum/lnworker.py b/electrum/lnworker.py
index 37aa6c98a..ffc56c74f 100644
--- a/electrum/lnworker.py
+++ b/electrum/lnworker.py
@@ -338,6 +338,7 @@ class LNWorker(Logger, EventListener, NetworkRetryManager[LNPeerAddr]):
 
     def start_network(self, network: 'Network'):
         assert network
+        assert self.network is None, "already started"
         self.network = network
         self.config = network.config
         self._add_peers_from_config()
diff --git a/electrum/submarine_swaps.py b/electrum/submarine_swaps.py
index d1c653ca3..b0af03fd4 100644
--- a/electrum/submarine_swaps.py
+++ b/electrum/submarine_swaps.py
@@ -170,6 +170,7 @@ class SwapManager(Logger):
     def start_network(self, *, network: 'Network', lnwatcher: 'LNWalletWatcher'):
         assert network
         assert lnwatcher
+        assert self.network is None, "already started"
         self.network = network
         self.lnwatcher = lnwatcher
         for k, swap in self.swaps.items():
diff --git a/electrum/wallet.py b/electrum/wallet.py
index ec75dab95..302726f4b 100644
--- a/electrum/wallet.py
+++ b/electrum/wallet.py
@@ -440,7 +440,7 @@ class Abstract_Wallet(ABC, Logger, EventListener):
             self.db.put('lightning_privkey2', ln_xprv)
         self.lnworker = LNWallet(self, ln_xprv)
         if self.network:
-            self.start_network_lightning()
+            self._start_network_lightning()
 
     async def stop(self):
         """Stop all networking and save DB to disk."""
@@ -531,15 +531,16 @@ class Abstract_Wallet(ABC, Logger, EventListener):
         self.adb.clear_history()
         self.save_db()
 
-    def start_network(self, network):
+    def start_network(self, network: 'Network'):
+        assert self.network is None, "already started"
         self.network = network
         if network:
             asyncio.run_coroutine_threadsafe(self.main_loop(), self.network.asyncio_loop)
             self.adb.start_network(network)
             if self.lnworker:
-                self.start_network_lightning()
+                self._start_network_lightning()
 
-    def start_network_lightning(self):
+    def _start_network_lightning(self):
         assert self.lnworker
         assert self.lnworker.network is None, 'lnworker network already initialized'
         self.lnworker.start_network(self.network)