diff --git a/electrum/tests/test_verifier.py b/electrum/tests/test_verifier.py
index 464f39b19..009de2ab9 100644
--- a/electrum/tests/test_verifier.py
+++ b/electrum/tests/test_verifier.py
@@ -8,71 +8,43 @@ from electrum.verifier import SPV, InnerNodeOfSpvProofIsValidTx
 from . import TestCaseForTestnet
 
 
-TST_MBRANCH = [
+MERKLE_BRANCH = [
     'f2994fd4546086b21b4916b76cf901afb5c4db1c3ecbfc91d6f4cae1186dfe12',
     '6b65935528311901c7acda7db817bd6e3ce2f05d1c62c385b7caadb65fac7520']
 
-TST_R = '11dbac015b6969ea75509dd1250f33c04ec4d562c2d895de139a65f62f808254'
+MERKLE_ROOT = '11dbac015b6969ea75509dd1250f33c04ec4d562c2d895de139a65f62f808254'
 
-TEST_T_TX_RAW = ('0200000001cb659c5528311901a7aada'
-                 '7db817bd6e3ce2f05d1c62c385b7caad'
-                 'b65fac75201234000000fabcdefa01ab'
-                 'cd1234010000000405060708fabcdefa')
-
-ORIG_RAISE_IF_VALID_TX = SPV._raise_if_valid_tx
+VALID_64_BYTE_TX = ('0200000001cb659c5528311901a7aada7db817bd6e3ce2f05d1c62c385b7caad'
+                    'b65fac75201234000000fabcdefa01abcd1234010000000405060708fabcdefa')
+assert len(VALID_64_BYTE_TX) == 128
 
 
 class VerifierTestCase(TestCaseForTestnet):
+    # these tests are regarding the attack described in
+    # https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2018-June/016105.html
 
     def test_verify_ok_t_tx(self):
-        '''test vefify ok forged T tx'''
-        assert len(TEST_T_TX_RAW) == 128
-        t_tx = Transaction(TEST_T_TX_RAW)
+        """Actually mined 64 byte tx should not raise."""
+        t_tx = Transaction(VALID_64_BYTE_TX)
         t_tx_hash = t_tx.txid()
-        assert SPV.hash_merkle_root(TST_MBRANCH, t_tx_hash, 3) == TST_R
-
-    def test_verify_ok_f_tx(self):
-        '''test verify ok forged F tx (fake)'''
-        SPV._raise_if_valid_tx = lambda raw_tx: None
-        t_tx = Transaction(TEST_T_TX_RAW)
-        # first 32 bytes of T encoded as hash
-        fake_branch_node = hash_encode(bfh(TEST_T_TX_RAW[:64]))
-        fake_mbranch = [fake_branch_node] + TST_MBRANCH
-        # last 32 bytes of T encoded as hash
-        f_tx_hash = hash_encode(bfh(TEST_T_TX_RAW[64:]))
-        assert SPV.hash_merkle_root(fake_mbranch, f_tx_hash, 7) == TST_R
-        SPV._raise_if_valid_tx = ORIG_RAISE_IF_VALID_TX
+        self.assertEqual(MERKLE_ROOT, SPV.hash_merkle_root(MERKLE_BRANCH, t_tx_hash, 3))
 
-    def test_verify_fail_f_tx(self):
-        '''test verify fail forged F tx (fake)'''
-        t_tx = Transaction(TEST_T_TX_RAW)
+    def test_verify_fail_f_tx_odd(self):
+        """Raise if inner node of merkle branch is valid tx. ('odd' fake leaf position)"""
         # first 32 bytes of T encoded as hash
-        fake_branch_node = hash_encode(bfh(TEST_T_TX_RAW[:64]))
-        fake_mbranch = [fake_branch_node] + TST_MBRANCH
+        fake_branch_node = hash_encode(bfh(VALID_64_BYTE_TX[:64]))
+        fake_mbranch = [fake_branch_node] + MERKLE_BRANCH
         # last 32 bytes of T encoded as hash
-        f_tx_hash = hash_encode(bfh(TEST_T_TX_RAW[64:]))
+        f_tx_hash = hash_encode(bfh(VALID_64_BYTE_TX[64:]))
         with self.assertRaises(InnerNodeOfSpvProofIsValidTx):
-            assert SPV.hash_merkle_root(fake_mbranch, f_tx_hash, 7) == TST_R
-
-    def test_verify_ok_f_tx_even(self):
-        '''test verify ok forged F tx (fake) with even fake txpos'''
-        SPV._raise_if_valid_tx = lambda raw_tx: None
-        t_tx = Transaction(TEST_T_TX_RAW)
-        # last 32 bytes of T encoded as hash
-        fake_branch_node = hash_encode(bfh(TEST_T_TX_RAW[64:]))
-        fake_mbranch = [fake_branch_node] + TST_MBRANCH
-        # first 32 bytes of T encoded as hash
-        f_tx_hash = hash_encode(bfh(TEST_T_TX_RAW[:64]))
-        assert SPV.hash_merkle_root(fake_mbranch, f_tx_hash, 6) == TST_R
-        SPV._raise_if_valid_tx = ORIG_RAISE_IF_VALID_TX
+            SPV.hash_merkle_root(fake_mbranch, f_tx_hash, 7)
 
     def test_verify_fail_f_tx_even(self):
-        '''test verify fail forged F tx (fake) with even fake txpos'''
-        t_tx = Transaction(TEST_T_TX_RAW)
+        """Raise if inner node of merkle branch is valid tx. ('even' fake leaf position)"""
         # last 32 bytes of T encoded as hash
-        fake_branch_node = hash_encode(bfh(TEST_T_TX_RAW[64:]))
-        fake_mbranch = [fake_branch_node] + TST_MBRANCH
+        fake_branch_node = hash_encode(bfh(VALID_64_BYTE_TX[64:]))
+        fake_mbranch = [fake_branch_node] + MERKLE_BRANCH
         # first 32 bytes of T encoded as hash
-        f_tx_hash = hash_encode(bfh(TEST_T_TX_RAW[:64]))
+        f_tx_hash = hash_encode(bfh(VALID_64_BYTE_TX[:64]))
         with self.assertRaises(InnerNodeOfSpvProofIsValidTx):
-            assert SPV.hash_merkle_root(fake_mbranch, f_tx_hash, 6) == TST_R
+            SPV.hash_merkle_root(fake_mbranch, f_tx_hash, 6)
diff --git a/electrum/verifier.py b/electrum/verifier.py
index eb00916ae..01a0eb8db 100644
--- a/electrum/verifier.py
+++ b/electrum/verifier.py
@@ -149,7 +149,7 @@ class SPV(NetworkJobOnDefaultServer):
         for item in merkle_branch_bytes:
             if len(item) != 32:
                 raise MerkleVerificationFailure('all merkle branch items have to 32 bytes long')
-            inner_node = item + h if index & 1 else h + item
+            inner_node = (item + h) if (index & 1) else (h + item)
             cls._raise_if_valid_tx(bh2u(inner_node))
             h = sha256d(inner_node)
             index >>= 1