diff --git a/python/CHANGELOG.md b/python/CHANGELOG.md
index 09507b3e0e..486576a119 100644
--- a/python/CHANGELOG.md
+++ b/python/CHANGELOG.md
@@ -19,6 +19,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 - protobuf is aware of `required` fields and default values
 - `btc.sign_tx()` accepts keyword arguments for transaction metadata  [#1266]
+- Support long PIN of up to 50 digits.  [#1167]
 
 ### Deprecated
 
@@ -509,6 +510,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 [#948]: https://github.com/trezor/trezor-firmware/issues/948
 [#1052]: https://github.com/trezor/trezor-firmware/issues/1052
 [#1126]: https://github.com/trezor/trezor-firmware/issues/1126
+[#1167]: https://github.com/trezor/trezor-firmware/issues/1167
 [#1179]: https://github.com/trezor/trezor-firmware/issues/1179
 [#1196]: https://github.com/trezor/trezor-firmware/issues/1196
 [#1210]: https://github.com/trezor/trezor-firmware/issues/1210
diff --git a/python/src/trezorlib/client.py b/python/src/trezorlib/client.py
index a75be139a2..cd10380e01 100644
--- a/python/src/trezorlib/client.py
+++ b/python/src/trezorlib/client.py
@@ -29,6 +29,7 @@ LOG = logging.getLogger(__name__)
 
 VENDORS = ("bitcointrezor.com", "trezor.io")
 MAX_PASSPHRASE_LENGTH = 50
+MAX_PIN_LENGTH = 50
 
 PASSPHRASE_ON_DEVICE = object()
 PASSPHRASE_TEST_PATH = tools.parse_path("44h/1h/0h/0/0")
@@ -152,7 +153,9 @@ class TrezorClient:
             self.call_raw(messages.Cancel())
             raise
 
-        if any(d not in "123456789" for d in pin) or not (1 <= len(pin) <= 9):
+        if any(d not in "123456789" for d in pin) or not (
+            1 <= len(pin) <= MAX_PIN_LENGTH
+        ):
             self.call_raw(messages.Cancel())
             raise ValueError("Invalid PIN provided")
 
diff --git a/python/src/trezorlib/ui.py b/python/src/trezorlib/ui.py
index 479d76f91b..bbdf09fa59 100644
--- a/python/src/trezorlib/ui.py
+++ b/python/src/trezorlib/ui.py
@@ -20,7 +20,7 @@ import click
 from mnemonic import Mnemonic
 
 from . import device
-from .client import PASSPHRASE_ON_DEVICE
+from .client import MAX_PIN_LENGTH, PASSPHRASE_ON_DEVICE
 from .exceptions import Cancelled
 from .messages import PinMatrixRequestType, WordRequestType
 
@@ -107,8 +107,12 @@ class ClickUI:
                 echo(
                     "The value may only consist of digits 1 to 9 or letters cvbdfgert."
                 )
-            elif len(pin) > 9:
-                echo("The value must be at most 9 digits in length.")
+            elif len(pin) > MAX_PIN_LENGTH:
+                echo(
+                    "The value must be at most {} digits in length.".format(
+                        MAX_PIN_LENGTH
+                    )
+                )
             else:
                 return pin