diff --git a/test/functional/feature_nulldummy.py b/test/functional/feature_nulldummy.py
index f467626801..0f2d47f4b1 100755
--- a/test/functional/feature_nulldummy.py
+++ b/test/functional/feature_nulldummy.py
@@ -24,7 +24,10 @@ from test_framework.blocktools import (
 from test_framework.messages import CTransaction
 from test_framework.script import CScript
 from test_framework.test_framework import BitcoinTestFramework
-from test_framework.util import assert_equal, assert_raises_rpc_error
+from test_framework.util import (
+    assert_equal,
+    assert_raises_rpc_error,
+)
 
 NULLDUMMY_ERROR = "non-mandatory-script-verify-flag (Dummy CHECKMULTISIG argument must be zero)"
 
@@ -86,7 +89,7 @@ class NULLDUMMYTest(BitcoinTestFramework):
         txid2 = self.nodes[0].sendrawtransaction(test1txs[1].serialize_with_witness().hex(), 0)
         test1txs.append(create_transaction(self.nodes[0], coinbase_txid[1], self.wit_ms_address, amount=49))
         txid3 = self.nodes[0].sendrawtransaction(test1txs[2].serialize_with_witness().hex(), 0)
-        self.block_submit(self.nodes[0], test1txs, False, True)
+        self.block_submit(self.nodes[0], test1txs, accept=True)
 
         self.log.info("Test 2: Non-NULLDUMMY base multisig transaction should not be accepted to mempool before activation")
         test2tx = create_transaction(self.nodes[0], txid2, self.ms_address, amount=47)
@@ -94,28 +97,28 @@ class NULLDUMMYTest(BitcoinTestFramework):
         assert_raises_rpc_error(-26, NULLDUMMY_ERROR, self.nodes[0].sendrawtransaction, test2tx.serialize_with_witness().hex(), 0)
 
         self.log.info(f"Test 3: Non-NULLDUMMY base transactions should be accepted in a block before activation [{COINBASE_MATURITY + 4}]")
-        self.block_submit(self.nodes[0], [test2tx], False, True)
+        self.block_submit(self.nodes[0], [test2tx], accept=True)
 
         self.log.info("Test 4: Non-NULLDUMMY base multisig transaction is invalid after activation")
         test4tx = create_transaction(self.nodes[0], test2tx.hash, self.address, amount=46)
         test6txs = [CTransaction(test4tx)]
         trueDummy(test4tx)
         assert_raises_rpc_error(-26, NULLDUMMY_ERROR, self.nodes[0].sendrawtransaction, test4tx.serialize_with_witness().hex(), 0)
-        self.block_submit(self.nodes[0], [test4tx])
+        self.block_submit(self.nodes[0], [test4tx], accept=False)
 
         self.log.info("Test 5: Non-NULLDUMMY P2WSH multisig transaction invalid after activation")
         test5tx = create_transaction(self.nodes[0], txid3, self.wit_address, amount=48)
         test6txs.append(CTransaction(test5tx))
         test5tx.wit.vtxinwit[0].scriptWitness.stack[0] = b'\x01'
         assert_raises_rpc_error(-26, NULLDUMMY_ERROR, self.nodes[0].sendrawtransaction, test5tx.serialize_with_witness().hex(), 0)
-        self.block_submit(self.nodes[0], [test5tx], True)
+        self.block_submit(self.nodes[0], [test5tx], with_witness=True, accept=False)
 
         self.log.info(f"Test 6: NULLDUMMY compliant base/witness transactions should be accepted to mempool and in block after activation [{COINBASE_MATURITY + 5}]")
         for i in test6txs:
             self.nodes[0].sendrawtransaction(i.serialize_with_witness().hex(), 0)
-        self.block_submit(self.nodes[0], test6txs, True, True)
+        self.block_submit(self.nodes[0], test6txs, with_witness=True, accept=True)
 
-    def block_submit(self, node, txs, witness=False, accept=False):
+    def block_submit(self, node, txs, *, with_witness=False, accept):
         tmpl = node.getblocktemplate(NORMAL_GBT_REQUEST_PARAMS)
         assert_equal(tmpl['previousblockhash'], self.lastblockhash)
         assert_equal(tmpl['height'], self.lastblockheight + 1)
@@ -124,11 +127,12 @@ class NULLDUMMYTest(BitcoinTestFramework):
             tx.rehash()
             block.vtx.append(tx)
         block.hashMerkleRoot = block.calc_merkle_root()
-        witness and add_witness_commitment(block)
+        if with_witness:
+            add_witness_commitment(block)
         block.rehash()
         block.solve()
         assert_equal(None if accept else 'block-validation-failed', node.submitblock(block.serialize().hex()))
-        if (accept):
+        if accept:
             assert_equal(node.getbestblockhash(), block.hash)
             self.lastblockhash = block.hash
             self.lastblocktime += 1