diff --git a/electrum/submarine_swaps.py b/electrum/submarine_swaps.py
index b3248b41d..5f36f1fd9 100644
--- a/electrum/submarine_swaps.py
+++ b/electrum/submarine_swaps.py
@@ -1413,7 +1413,7 @@ class NostrTransport(Logger):
             'min_amount': sm._min_amount,
             'max_amount': sm._max_amount,
             'relays': sm.config.NOSTR_RELAYS,
-            'pow_nonce': str(sm.config.SWAPSERVER_ANN_POW_NONCE),
+            'pow_nonce': hex(sm.config.SWAPSERVER_ANN_POW_NONCE),
         }
         # the first value of a single letter tag is indexed and can be filtered for
         tags = [['d', f'electrum-swapserver-{self.NOSTR_EVENT_VERSION}'],
@@ -1470,7 +1470,13 @@ class NostrTransport(Logger):
             if event.created_at <= ts:
                 #print('skipping old event', pubkey[0:10], event.id)
                 continue
-            pow_bits = get_nostr_ann_pow_amount(bytes.fromhex(pubkey), int(content.get('pow_nonce', 0)))
+            try:
+                pow_bits = get_nostr_ann_pow_amount(
+                    bytes.fromhex(pubkey),
+                    int(content.get('pow_nonce', "0"), 16)
+                )
+            except ValueError:
+                continue
             if pow_bits < self.config.SWAPSERVER_POW_TARGET:
                 self.logger.debug(f"too low pow: {pubkey}: pow: {pow_bits} nonce: {content.get('pow_nonce', 0)}")
                 continue
diff --git a/electrum/util.py b/electrum/util.py
index b593dfe83..0aca54f49 100644
--- a/electrum/util.py
+++ b/electrum/util.py
@@ -2127,7 +2127,7 @@ def nostr_pow_worker(nonce, nostr_pubk, target_bits, hash_function, hash_len_bit
         # we cannot check is_set on each iteration as it has a lot of overhead, this way we can check
         # it with low overhead (just the additional range counter)
         for i in range(1000000):
-            digest = hash_function(hash_preimage + nonce.to_bytes(8, 'big')).digest()
+            digest = hash_function(hash_preimage + nonce.to_bytes(32, 'big')).digest()
             if int.from_bytes(digest, 'big') < (1 << (hash_len_bits - target_bits)):
                 shutdown.set()
                 return hash, nonce
@@ -2141,7 +2141,7 @@ async def gen_nostr_ann_pow(nostr_pubk: bytes, target_bits: int) -> Tuple[int, i
     import multiprocessing  # not available on Android, so we import it here
     hash_function = hashlib.sha256
     hash_len_bits = 256
-    max_nonce = 0xFFFFFFFFFFFFFFFF  # 8 byte
+    max_nonce: int = (1 << (32 * 8)) - 1  # 32-byte nonce
     start_nonce = 0
 
     max_workers = max(multiprocessing.cpu_count() - 1, 1)  # use all but one CPU
@@ -2181,6 +2181,6 @@ def get_nostr_ann_pow_amount(nostr_pubk: bytes, nonce: Optional[int]) -> int:
     hash_len_bits = 256
     hash_preimage = b'electrum-' + nostr_pubk
 
-    digest = hash_function(hash_preimage + nonce.to_bytes(8, 'big')).digest()
+    digest = hash_function(hash_preimage + nonce.to_bytes(32, 'big')).digest()
     digest = int.from_bytes(digest, 'big')
     return hash_len_bits - digest.bit_length()