diff --git a/electrum/synchronizer.py b/electrum/synchronizer.py
index 9d619b47e..7f31de859 100644
--- a/electrum/synchronizer.py
+++ b/electrum/synchronizer.py
@@ -61,6 +61,10 @@ class SynchronizerBase(NetworkJobOnDefaultServer):
     def __init__(self, network: 'Network'):
         self.asyncio_loop = network.asyncio_loop
         self._reset_request_counters()
+        # Ensure fairness between Synchronizers. e.g. if multiple wallets
+        # are open, a large wallet should not starve the small wallets:
+        self._network_request_semaphore = asyncio.Semaphore(100)
+
         NetworkJobOnDefaultServer.__init__(self, network)
 
     def _reset(self):
@@ -106,7 +110,8 @@ class SynchronizerBase(NetworkJobOnDefaultServer):
             self.scripthash_to_address[h] = addr
             self._requests_sent += 1
             try:
-                await self.session.subscribe('blockchain.scripthash.subscribe', [h], self.status_queue)
+                async with self._network_request_semaphore:
+                    await self.session.subscribe('blockchain.scripthash.subscribe', [h], self.status_queue)
             except RPCError as e:
                 if e.message == 'history too large':  # no unique error code
                     raise GracefulDisconnect(e, log_level=logging.ERROR) from e
@@ -167,7 +172,8 @@ class Synchronizer(SynchronizerBase):
         self.requested_histories.add((addr, status))
         h = address_to_scripthash(addr)
         self._requests_sent += 1
-        result = await self.interface.get_history_for_scripthash(h)
+        async with self._network_request_semaphore:
+            result = await self.interface.get_history_for_scripthash(h)
         self._requests_answered += 1
         self.logger.info(f"receiving history {addr} {len(result)}")
         hashes = set(map(lambda item: item['tx_hash'], result))
@@ -210,7 +216,8 @@ class Synchronizer(SynchronizerBase):
     async def _get_transaction(self, tx_hash, *, allow_server_not_finding_tx=False):
         self._requests_sent += 1
         try:
-            raw_tx = await self.interface.get_transaction(tx_hash)
+            async with self._network_request_semaphore:
+                raw_tx = await self.interface.get_transaction(tx_hash)
         except RPCError as e:
             # most likely, "No such mempool or blockchain transaction"
             if allow_server_not_finding_tx: