diff --git a/core/src/apps/cardano/helpers/protocol_magics.py b/core/src/apps/cardano/helpers/protocol_magics.py
index dc05388966..cc5c567e8a 100644
--- a/core/src/apps/cardano/helpers/protocol_magics.py
+++ b/core/src/apps/cardano/helpers/protocol_magics.py
@@ -1,5 +1,5 @@
 MAINNET = 764824073
-TESTNET = 42
+TESTNET = 1097911063
 
 NAMES = {
     MAINNET: "Mainnet",
diff --git a/core/tests/test_apps.cardano.address.py b/core/tests/test_apps.cardano.address.py
index 67c94870bc..40d784ce98 100644
--- a/core/tests/test_apps.cardano.address.py
+++ b/core/tests/test_apps.cardano.address.py
@@ -279,9 +279,9 @@ class TestCardanoAddress(unittest.TestCase):
 
     def test_testnet_byron_address(self):
         addresses = [
-            "2657WMsDfac5F3zbgs9BwNWx3dhGAJERkAL93gPa68NJ2i8mbCHm2pLUHWSj8Mfea",
-            "2657WMsDfac6ezKWszxLFqJjSUgpg9NgxKc1koqi24sVpRaPhiwMaExk4useKn5HA",
-            "2657WMsDfac7hr1ioJGr6g7r6JRx4r1My8Rj91tcPTeVjJDpfBYKURrPG2zVLx2Sq",
+            "2cWKMJemoBajmHz9haobccjHnxiynESe2hqtza25GBgHpKAtE8BpvUgd3ixRzrAvMjgfo",
+            "2cWKMJemoBakg9bfV8iHwNxF4TtoJVUsFMGZPJ2e1xnLLZ12WTcvYbTZg2eeXMBZmkrA1",
+            "2cWKMJemoBakYYADj3dviYVXQhzHxdDEHdsnkJfSYevd3wZi8eneSzEGRmXNvNDjYdjBw",
         ]
 
         for i, expected in enumerate(addresses):
diff --git a/python/src/trezorlib/cardano.py b/python/src/trezorlib/cardano.py
index cef8f94248..d49dcfc1e7 100644
--- a/python/src/trezorlib/cardano.py
+++ b/python/src/trezorlib/cardano.py
@@ -36,7 +36,7 @@ if TYPE_CHECKING:
     from .client import TrezorClient
     from .protobuf import MessageType
 
-PROTOCOL_MAGICS = {"mainnet": 764824073, "testnet": 42}
+PROTOCOL_MAGICS = {"mainnet": 764824073, "testnet": 1097911063}
 NETWORK_IDS = {"mainnet": 1, "testnet": 0}
 
 REQUIRED_FIELDS_TRANSACTION = ("inputs", "outputs")