diff --git a/src/apps/monero/protocol/signing/step_07_all_out1_set.py b/src/apps/monero/protocol/signing/step_07_all_out1_set.py
index b5d5b180a..437bbfbb6 100644
--- a/src/apps/monero/protocol/signing/step_07_all_out1_set.py
+++ b/src/apps/monero/protocol/signing/step_07_all_out1_set.py
@@ -93,11 +93,9 @@ def _set_tx_extra(state: State):
 
     state.tx.extra = tsx_helper.add_tx_pub_key_to_extra(state.tx.extra, state.tx_pub)
 
-    # Not needed to remove - extra is clean
-    # state.tx.extra = await monero.remove_field_from_tx_extra(state.tx.extra, xmrtypes.TxExtraAdditionalPubKeys)
     if state.need_additional_txkeys:
         state.tx.extra = tsx_helper.add_additional_tx_pub_keys_to_extra(
-            state.tx.extra, pub_enc=state.additional_tx_public_keys
+            state.tx.extra, state.additional_tx_public_keys
         )
 
 
diff --git a/src/apps/monero/xmr/serialize_messages/tx_extra.py b/src/apps/monero/xmr/serialize_messages/tx_extra.py
deleted file mode 100644
index ac438d608..000000000
--- a/src/apps/monero/xmr/serialize_messages/tx_extra.py
+++ /dev/null
@@ -1,35 +0,0 @@
-
-from apps.monero.xmr.serialize.message_types import (
-    BlobType,
-    ContainerType,
-    MessageType,
-    VariantType,
-)
-from apps.monero.xmr.serialize_messages.base import ECPublicKey
-
-
-class TxExtraNonce(MessageType):
-    __slots__ = ("nonce",)
-    VARIANT_CODE = 0x2
-
-    @classmethod
-    def f_specs(cls):
-        return (("nonce", BlobType),)
-
-
-class TxExtraAdditionalPubKeys(MessageType):
-    __slots__ = ("data",)
-    VARIANT_CODE = 0x4
-
-    @classmethod
-    def f_specs(cls):
-        return (("data", ContainerType, ECPublicKey),)
-
-
-class TxExtraField(VariantType):
-    @classmethod
-    def f_specs(cls):
-        return (
-            ("tx_extra_nonce", TxExtraNonce),
-            ("tx_extra_additional_pub_keys", TxExtraAdditionalPubKeys),
-        )
diff --git a/src/apps/monero/xmr/sub/tsx_helper.py b/src/apps/monero/xmr/sub/tsx_helper.py
index a0152749f..f8c7b8d54 100644
--- a/src/apps/monero/xmr/sub/tsx_helper.py
+++ b/src/apps/monero/xmr/sub/tsx_helper.py
@@ -1,10 +1,5 @@
 from apps.monero.xmr import crypto
-from apps.monero.xmr.serialize import xmrserialize
-from apps.monero.xmr.serialize.readwriter import MemoryReaderWriter
-from apps.monero.xmr.serialize_messages.tx_extra import (
-    TxExtraAdditionalPubKeys,
-    TxExtraField,
-)
+from apps.monero.xmr.serialize import int_serialize
 
 
 def absolute_output_offsets_to_relative(off):
@@ -25,27 +20,27 @@ def add_tx_pub_key_to_extra(tx_extra, pub_key):
     Adds public key to the extra
     """
     to_add = bytearray(33)
-    to_add[0] = 1
-    crypto.encodepoint_into(memoryview(to_add)[1:], pub_key)  # TX_EXTRA_TAG_PUBKEY
+    to_add[0] = 1  # TX_EXTRA_TAG_PUBKEY
+    crypto.encodepoint_into(memoryview(to_add)[1:], pub_key)
     return tx_extra + to_add
 
 
-def add_additional_tx_pub_keys_to_extra(
-    tx_extra, additional_pub_keys=None, pub_enc=None
-):
+def add_additional_tx_pub_keys_to_extra(tx_extra, pub_enc):
     """
-    Adds all pubkeys to the extra
+    Adds all additional tx public keys to the extra buffer
     """
-    pubs_msg = TxExtraAdditionalPubKeys(
-        data=pub_enc
-        if pub_enc
-        else [crypto.encodepoint(x) for x in additional_pub_keys]
-    )
+    # format: variant_tag (0x4) | array len varint | 32B | 32B | ...
+    num_keys = len(pub_enc)
+    len_size = int_serialize.uvarint_size(num_keys)
+    buffer = bytearray(1 + len_size + 32 * num_keys)
 
-    rw = MemoryReaderWriter()
-    ar = xmrserialize.Archive(rw, True)
+    buffer[0] = 0x4  # TX_EXTRA_TAG_ADDITIONAL_PUBKEYS
+    int_serialize.dump_uvarint_b_into(num_keys, buffer, 1)  # uvarint(num_keys)
+    offset = 1 + len_size
 
-    # format: variant_tag (0x4) | array len varint | 32B | 32B | ...
-    ar.variant(pubs_msg, TxExtraField)
-    tx_extra += rw.get_buffer()
+    for idx in range(num_keys):
+        buffer[offset : offset + 32] = pub_enc[idx]
+        offset += 32
+
+    tx_extra += buffer
     return tx_extra