diff --git a/tests/device_tests/test_msg_signtx_prevhash.py b/tests/device_tests/test_msg_signtx_prevhash.py
index 1da397c2c..b0aeaa688 100644
--- a/tests/device_tests/test_msg_signtx_prevhash.py
+++ b/tests/device_tests/test_msg_signtx_prevhash.py
@@ -61,22 +61,21 @@ def hash_tx(data: bytes) -> bytes:
 
 def _check_error_message(value: bytes, model: str, message: str):
     if model != "1":
-        if value is None:
-            assert message == "Failed to decode message: Missing"
-        else:
-            assert message == "Provided prev_hash is invalid."
-        return
+        assert message == "Provided prev_hash is invalid."
 
     # T1 has several possible errors
-    if value is None:
-        assert message.endswith("missing required field")
     elif len(value) > 32:
         assert message.endswith("bytes overflow")
     else:
         assert message.endswith("Encountered invalid prevhash")
 
 
-@pytest.mark.parametrize("prev_hash", (None, b"", b"x", b"hello world", b"x" * 33))
+with_bad_prevhashes = pytest.mark.parametrize(
+    "prev_hash", (b"", b"x", b"hello world", b"x" * 33)
+)
+
+
+@with_bad_prevhashes
 def test_invalid_prev_hash(client, prev_hash):
     inp1 = messages.TxInputType(
         address_n=tools.parse_path("m/44h/0h/0h/0/0"),
@@ -96,7 +95,7 @@ def test_invalid_prev_hash(client, prev_hash):
     _check_error_message(prev_hash, client.features.model, e.value.message)
 
 
-@pytest.mark.parametrize("prev_hash", (None, b"", b"x", b"hello world", b"x" * 33))
+@with_bad_prevhashes
 def test_invalid_prev_hash_attack(client, prev_hash):
     # prepare input with a valid prev-hash
     inp1 = messages.TxInputType(
@@ -138,7 +137,7 @@ def test_invalid_prev_hash_attack(client, prev_hash):
     _check_error_message(prev_hash, client.features.model, e.value.message)
 
 
-@pytest.mark.parametrize("prev_hash", (None, b"", b"x", b"hello world", b"x" * 33))
+@with_bad_prevhashes
 def test_invalid_prev_hash_in_prevtx(client, prev_hash):
     cache = TxCache("Bitcoin")
     prev_tx = cache[TXHASH_157041]
diff --git a/tests/ui_tests/fixtures.json b/tests/ui_tests/fixtures.json
index 891afdce7..df9112327 100644
--- a/tests/ui_tests/fixtures.json
+++ b/tests/ui_tests/fixtures.json
@@ -554,17 +554,14 @@
 "test_msg_signtx_peercoin.py::test_timestamp_included": "0e76606dba98b8389ef587f48c2ce65b66457d9b206eaecdda56a4e115e0c829",
 "test_msg_signtx_peercoin.py::test_timestamp_missing": "c09de07fbbf1e047442180e2facb5482d06a1a428891b875b7dd93c9e4704ae1",
 "test_msg_signtx_peercoin.py::test_timestamp_missing_prevtx": "fe6ecad8988b5c789419b9134317bbf018007c5005047dd9cba7b9655e56349c",
-"test_msg_signtx_prevhash.py::test_invalid_prev_hash[None]": "1c100ce4b7c1e47e72428f390de0846c1ff933e9f07894872644a369a9422738",
 "test_msg_signtx_prevhash.py::test_invalid_prev_hash[]": "1c100ce4b7c1e47e72428f390de0846c1ff933e9f07894872644a369a9422738",
 "test_msg_signtx_prevhash.py::test_invalid_prev_hash[hello world]": "1c100ce4b7c1e47e72428f390de0846c1ff933e9f07894872644a369a9422738",
 "test_msg_signtx_prevhash.py::test_invalid_prev_hash[x]": "1c100ce4b7c1e47e72428f390de0846c1ff933e9f07894872644a369a9422738",
 "test_msg_signtx_prevhash.py::test_invalid_prev_hash[xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx]": "1c100ce4b7c1e47e72428f390de0846c1ff933e9f07894872644a369a9422738",
-"test_msg_signtx_prevhash.py::test_invalid_prev_hash_attack[None]": "91fa0c1fdb411c207cc5e7bca8fed5ee82e98b4b1fc092e576ad225a0f74724f",
 "test_msg_signtx_prevhash.py::test_invalid_prev_hash_attack[]": "91fa0c1fdb411c207cc5e7bca8fed5ee82e98b4b1fc092e576ad225a0f74724f",
 "test_msg_signtx_prevhash.py::test_invalid_prev_hash_attack[hello world]": "91fa0c1fdb411c207cc5e7bca8fed5ee82e98b4b1fc092e576ad225a0f74724f",
 "test_msg_signtx_prevhash.py::test_invalid_prev_hash_attack[x]": "91fa0c1fdb411c207cc5e7bca8fed5ee82e98b4b1fc092e576ad225a0f74724f",
 "test_msg_signtx_prevhash.py::test_invalid_prev_hash_attack[xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx]": "91fa0c1fdb411c207cc5e7bca8fed5ee82e98b4b1fc092e576ad225a0f74724f",
-"test_msg_signtx_prevhash.py::test_invalid_prev_hash_in_prevtx[None]": "612cad5b3bb70a8aed99345fe2ce3058cd1a153521c0b8b8bf9f8d7c0b2c76a2",
 "test_msg_signtx_prevhash.py::test_invalid_prev_hash_in_prevtx[]": "612cad5b3bb70a8aed99345fe2ce3058cd1a153521c0b8b8bf9f8d7c0b2c76a2",
 "test_msg_signtx_prevhash.py::test_invalid_prev_hash_in_prevtx[hello world]": "612cad5b3bb70a8aed99345fe2ce3058cd1a153521c0b8b8bf9f8d7c0b2c76a2",
 "test_msg_signtx_prevhash.py::test_invalid_prev_hash_in_prevtx[x]": "612cad5b3bb70a8aed99345fe2ce3058cd1a153521c0b8b8bf9f8d7c0b2c76a2",