diff --git a/src/apps/wallet/sign_tx/helpers.py b/src/apps/wallet/sign_tx/helpers.py
index 78d62c3f8..d6ffb5ab5 100644
--- a/src/apps/wallet/sign_tx/helpers.py
+++ b/src/apps/wallet/sign_tx/helpers.py
@@ -107,8 +107,10 @@ def sanitize_tx_meta(tx: TransactionType) -> TransactionType:
 
 def sanitize_tx_input(tx: TransactionType) -> TxInputType:
     txi = tx.inputs[0]
-    txi.script_type = (
-        txi.script_type if txi.script_type is not None else InputScriptType.SPENDADDRESS)
+    if txi.script_type is None:
+        txi.script_type = InputScriptType.SPENDADDRESS
+    if txi.sequence is None:
+        txi.sequence = 4294967295
     return txi
 
 
diff --git a/src/apps/wallet/sign_tx/writers.py b/src/apps/wallet/sign_tx/writers.py
index 9564a6fab..a9e8423bf 100644
--- a/src/apps/wallet/sign_tx/writers.py
+++ b/src/apps/wallet/sign_tx/writers.py
@@ -1,3 +1,5 @@
+from micropython import const
+
 from trezor.messages.TxOutputBinType import TxOutputBinType
 from trezor.messages.TxInputType import TxInputType
 from trezor.crypto.hashlib import sha256
@@ -5,26 +7,22 @@ from trezor.crypto.hashlib import sha256
 # TX Serialization
 # ===
 
-_DEFAULT_SEQUENCE = 4294967295
-
 
 def write_tx_input(w, i: TxInputType):
-    i_sequence = i.sequence if i.sequence is not None else _DEFAULT_SEQUENCE
     write_bytes_rev(w, i.prev_hash)
     write_uint32(w, i.prev_index)
     write_varint(w, len(i.script_sig))
     write_bytes(w, i.script_sig)
-    write_uint32(w, i_sequence)
+    write_uint32(w, i.sequence)
 
 
 def write_tx_input_check(w, i: TxInputType):
-    i_sequence = i.sequence if i.sequence is not None else _DEFAULT_SEQUENCE
     write_bytes(w, i.prev_hash)
     write_uint32(w, i.prev_index)
     write_uint32(w, len(i.address_n))
     for n in i.address_n:
         write_uint32(w, n)
-    write_uint32(w, i_sequence)
+    write_uint32(w, i.sequence)
     i_amount = i.amount if i.amount is not None else 0
     write_uint32(w, i_amount)  # this is probably redundant, but better safe than sorry