diff --git a/src/apps/wallet/sign_tx/helpers.py b/src/apps/wallet/sign_tx/helpers.py
index 3574e097..f5effa51 100644
--- a/src/apps/wallet/sign_tx/helpers.py
+++ b/src/apps/wallet/sign_tx/helpers.py
@@ -5,7 +5,7 @@ from trezor.messages.TxInputType import TxInputType
 from trezor.messages.SignTx import SignTx
 from trezor.messages.TxRequest import TxRequest
 from trezor.messages.TransactionType import TransactionType
-from trezor.messages.RequestType import TXINPUT, TXOUTPUT, TXMETA, TXFINISHED
+from trezor.messages.RequestType import TXINPUT, TXOUTPUT, TXMETA, TXEXTRADATA, TXFINISHED
 from trezor.messages import InputScriptType
 
 # Machine instructions
@@ -55,6 +55,17 @@ def request_tx_meta(tx_req: TxRequest, tx_hash: bytes=None):
     return sanitize_tx_meta(ack.tx)
 
 
+def request_tx_extra_data(tx_req: TxRequest, offset: int, size: int, tx_hash: bytes=None):
+    tx_req.request_type = TXEXTRADATA
+    tx_req.details.extra_data_offset = offset
+    tx_req.details.extra_data_len = size
+    tx_req.details.tx_hash = tx_hash
+    tx_req.details.request_index = None
+    ack = yield tx_req
+    tx_req.serialized = None
+    return ack.tx.extra_data
+
+
 def request_tx_input(tx_req: TxRequest, i: int, tx_hash: bytes=None):
     tx_req.request_type = TXINPUT
     tx_req.details.request_index = i
@@ -101,6 +112,7 @@ def sanitize_tx_meta(tx: TransactionType) -> TransactionType:
     tx.lock_time = tx.lock_time if tx.lock_time is not None else 0
     tx.inputs_cnt = tx.inputs_cnt if tx.inputs_cnt is not None else 0
     tx.outputs_cnt = tx.outputs_cnt if tx.outputs_cnt is not None else 0
+    tx.extra_data_len = tx.extra_data_len if tx.extra_data_len is not None else 0
     return tx
 
 
diff --git a/src/apps/wallet/sign_tx/signing.py b/src/apps/wallet/sign_tx/signing.py
index fcc51897..64cfec8b 100644
--- a/src/apps/wallet/sign_tx/signing.py
+++ b/src/apps/wallet/sign_tx/signing.py
@@ -319,6 +319,13 @@ async def get_prevtx_output_value(tx_req: TxRequest, prev_hash: bytes, prev_inde
 
     write_uint32(txh, tx.lock_time)
 
+    ofs = 0
+    while ofs < tx.extra_data_len:
+        size = min(1024, tx.extra_data_len - ofs)
+        data = await request_tx_extra_data(tx_req, ofs, size, prev_hash)
+        write_bytes(txh, data)
+        ofs += len(data)
+
     if get_tx_hash(txh, True, True) != prev_hash:
         raise SigningError(FailureType.ProcessError,
                            'Encountered invalid prev_hash')
diff --git a/tests/test_apps.wallet.signtx.fee_threshold.py b/tests/test_apps.wallet.signtx.fee_threshold.py
index 511ba6ed..3c8190d5 100644
--- a/tests/test_apps.wallet.signtx.fee_threshold.py
+++ b/tests/test_apps.wallet.signtx.fee_threshold.py
@@ -23,7 +23,7 @@ class TestSignTxFeeThreshold(unittest.TestCase):
     def test_over_fee_threshold(self):
         coin_bitcoin = coins.by_name('Bitcoin')
 
-        ptx1 = TransactionType(version=1, lock_time=0, inputs_cnt=2, outputs_cnt=1)
+        ptx1 = TransactionType(version=1, lock_time=0, inputs_cnt=2, outputs_cnt=1, extra_data_len=0)
         pinp1 = TxInputType(script_sig=unhexlify('483045022072ba61305fe7cb542d142b8f3299a7b10f9ea61f6ffaab5dca8142601869d53c0221009a8027ed79eb3b9bc13577ac2853269323434558528c6b6a7e542be46e7e9a820141047a2d177c0f3626fc68c53610b0270fa6156181f46586c679ba6a88b34c6f4874686390b4d92e5769fbb89c8050b984f4ec0b257a0e5c4ff8bd3b035a51709503'),
                             prev_hash=unhexlify('c16a03f1cf8f99f6b5297ab614586cacec784c2d259af245909dedb0e39eddcf'),
                             prev_index=1,
@@ -85,7 +85,7 @@ class TestSignTxFeeThreshold(unittest.TestCase):
     def test_under_threshold(self):
         coin_bitcoin = coins.by_name('Bitcoin')
 
-        ptx1 = TransactionType(version=1, lock_time=0, inputs_cnt=2, outputs_cnt=1)
+        ptx1 = TransactionType(version=1, lock_time=0, inputs_cnt=2, outputs_cnt=1, extra_data_len=0)
         pinp1 = TxInputType(script_sig=unhexlify('483045022072ba61305fe7cb542d142b8f3299a7b10f9ea61f6ffaab5dca8142601869d53c0221009a8027ed79eb3b9bc13577ac2853269323434558528c6b6a7e542be46e7e9a820141047a2d177c0f3626fc68c53610b0270fa6156181f46586c679ba6a88b34c6f4874686390b4d92e5769fbb89c8050b984f4ec0b257a0e5c4ff8bd3b035a51709503'),
                             prev_hash=unhexlify('c16a03f1cf8f99f6b5297ab614586cacec784c2d259af245909dedb0e39eddcf'),
                             prev_index=1,
diff --git a/tests/test_apps.wallet.signtx.py b/tests/test_apps.wallet.signtx.py
index 4f080ea4..e7920183 100644
--- a/tests/test_apps.wallet.signtx.py
+++ b/tests/test_apps.wallet.signtx.py
@@ -26,7 +26,7 @@ class TestSignTx(unittest.TestCase):
 
         coin_bitcoin = coins.by_name('Bitcoin')
 
-        ptx1 = TransactionType(version=1, lock_time=0, inputs_cnt=2, outputs_cnt=1)
+        ptx1 = TransactionType(version=1, lock_time=0, inputs_cnt=2, outputs_cnt=1, extra_data_len=0)
         pinp1 = TxInputType(script_sig=unhexlify('483045022072ba61305fe7cb542d142b8f3299a7b10f9ea61f6ffaab5dca8142601869d53c0221009a8027ed79eb3b9bc13577ac2853269323434558528c6b6a7e542be46e7e9a820141047a2d177c0f3626fc68c53610b0270fa6156181f46586c679ba6a88b34c6f4874686390b4d92e5769fbb89c8050b984f4ec0b257a0e5c4ff8bd3b035a51709503'),
                             prev_hash=unhexlify('c16a03f1cf8f99f6b5297ab614586cacec784c2d259af245909dedb0e39eddcf'),
                             prev_index=1,