diff --git a/jmclient/jmclient/blockchaininterface.py b/jmclient/jmclient/blockchaininterface.py
index 2cb16f9f9..e36a66456 100644
--- a/jmclient/jmclient/blockchaininterface.py
+++ b/jmclient/jmclient/blockchaininterface.py
@@ -70,14 +70,14 @@ def _estimate_fee_basic(self, conf_target: int) -> Optional[int]:
         or None in case of error.
         """
 
-    def _fee_per_kb_has_been_manually_set(self, N: int) -> bool:
-        """If the 'block' target is higher than 1000, interpret it
+    def _fee_per_kb_has_been_manually_set(self, tx_fees: int) -> bool:
+        """If the block target (tx_fees) is higher than 1000, interpret it
         as manually set fee sats/kvB.
         """
-        return N > 1000
+        return tx_fees > 1000
 
-    def estimate_fee_per_kb(self, N: int) -> int:
-        """ The argument N may be either a number of blocks target,
+    def estimate_fee_per_kb(self, tx_fees: int) -> int:
+        """ The argument tx_fees may be either a number of blocks target,
         for estimation of feerate by Core, or a number of satoshis
         per kilo-vbyte (see `_fee_per_kb_has_been_manually_set` for
         how this is distinguished).
@@ -101,8 +101,8 @@ def estimate_fee_per_kb(self, N: int) -> int:
         mempoolminfee_in_sat_randomized = random.uniform(
             mempoolminfee_in_sat, mempoolminfee_in_sat * float(1 + tx_fees_factor))
 
-        if self._fee_per_kb_has_been_manually_set(N):
-            N_res = random.uniform(N, N * float(1 - tx_fees_factor))
+        if self._fee_per_kb_has_been_manually_set(tx_fees):
+            N_res = random.uniform(tx_fees, tx_fees * float(1 - tx_fees_factor))
             if N_res < mempoolminfee_in_sat:
                 msg = "Using this mempool min fee as tx feerate"
                 if tx_fees_factor != 0:
@@ -117,7 +117,7 @@ def estimate_fee_per_kb(self, N: int) -> int:
                 log.info(msg + ": " + btc.fee_per_kb_to_str(N_res) + ".")
                 return int(N_res)
 
-        retval = self._estimate_fee_basic(N)
+        retval = self._estimate_fee_basic(tx_fees)
         if retval is None:
             log.warn("Falling back to default: " +
                 btc.fee_per_kb_to_str(fallback_fee) + ".")
@@ -134,7 +134,7 @@ def estimate_fee_per_kb(self, N: int) -> int:
                 mempoolminfee_in_sat_randomized) + ".")
             return int(mempoolminfee_in_sat_randomized)
         else:
-            msg = "Using bitcoin network feerate for " + str(N) + \
+            msg = "Using bitcoin network feerate for " + str(tx_fees) + \
                 " block confirmation target"
             if tx_fees_factor != 0:
                 msg = msg + " (randomized for privacy)"
@@ -466,13 +466,13 @@ def _get_mempool_min_fee(self) -> Optional[int]:
             return None
         return btc.btc_to_sat(rpc_result['mempoolminfee'])
 
-    def _estimate_fee_basic(self, N: int) -> Optional[int]:
+    def _estimate_fee_basic(self, tx_fees: int) -> Optional[int]:
         # Special bitcoin core case: sometimes the highest priority
         # cannot be estimated in that case the 2nd highest priority
         # should be used instead of falling back to hardcoded values
-        tries = 2 if N == 1 else 1
+        tries = 2 if tx_fees == 1 else 1
         for i in range(tries):
-            rpc_result = self._rpc('estimatesmartfee', [N + i])
+            rpc_result = self._rpc('estimatesmartfee', [tx_fees + i])
             if not rpc_result:
                 # in case of connection error:
                 return None
@@ -681,9 +681,9 @@ def __init__(self, jsonRpc, wallet_name):
         self.shutdown_signal = False
         self.destn_addr = self._rpc("getnewaddress", [])
 
-    def estimate_fee_per_kb(self, N: int) -> int:
+    def estimate_fee_per_kb(self, tx_fees: int) -> int:
         if not self.absurd_fees:
-            return super().estimate_fee_per_kb(N)
+            return super().estimate_fee_per_kb(tx_fees)
         else:
             return jm_single().config.getint("POLICY",
                                              "absurd_fee_per_kb") + 100
diff --git a/jmclient/test/commontest.py b/jmclient/test/commontest.py
index 2827264f5..530bc8ea5 100644
--- a/jmclient/test/commontest.py
+++ b/jmclient/test/commontest.py
@@ -135,7 +135,7 @@ def query_utxo_set(self, txouts, includeconfs=False):
             result.append(result_dict)        
         return result
 
-    def estimate_fee_per_kb(self, N: int) -> int:
+    def estimate_fee_per_kb(self, tx_fees: int) -> int:
         return 30000