README                           |  2 ++
 news.texi                        |  5 +++++
 pygost/__init__.py               |  2 +-
 pygost/gost3410.py               | 16 ++++++++++++++++
 pygost/stubs/pygost/gost3410.pyi |  3 +++
 pygost/test_gost3410.py          |  8 +++++---

diff --git a/README b/README
index de5ca5fe42bc2ae756afc4292e1c7a99eb489d515a8f9dac337d50e46a280bf3..2f025ec46d603f48a1dc7f7a86517532f1a93af4dfc1b8c5182c1899c1f61349 100644
--- a/README
+++ b/README
@@ -39,7 +39,9 @@     >>> curve = CURVES["id-tc26-gost-3410-12-512-paramSetA"]
     >>> from os import urandom
     >>> prv_raw = urandom(64)
     >>> from pygost.gost3410 import prv_unmarshal
+    >>> from pygost.gost3410 import prv_marshal
     >>> prv = prv_unmarshal(prv_raw)
+    >>> prv_raw = prv_marshal(curve, prv)
     >>> from pygost.gost3410 import public_key
     >>> pub = public_key(curve, prv)
     >>> from pygost.gost3410 import pub_marshal
diff --git a/news.texi b/news.texi
index 23d369cf031ea06070743486646ffb8dbc1cb025ebabfe82eb3af3a32737350c..bd99b4081c16d2dfc76ab7a2dd7bb81cb7c35a91c7712fb3ff317d2ef66be68e 100644
--- a/news.texi
+++ b/news.texi
@@ -3,6 +3,11 @@ @unnumbered News
 
 @table @strong
 
+@anchor{Release 5.4}
+@item 5.4
+@item @code{gost3410.prv_marshal} helper can make private keys that are
+in curve's Q field, for better compatibility with some implementations.
+
 @anchor{Release 5.3}
 @item 5.3
     @itemize
diff --git a/pygost/__init__.py b/pygost/__init__.py
index c1e43a5fe7109eb25b761cc0ff3b7a1067497b401c696107557bf668c14dd56e..3be0a5cf7b60ee6e473b355ad95b44f8bb8cdc3dd6be1fa5f54bbe44afa4c302 100644
--- a/pygost/__init__.py
+++ b/pygost/__init__.py
@@ -3,4 +3,4 @@
 PyGOST is free software: see the file COPYING for copying conditions.
 """
 
-__version__ = "5.3"
+__version__ = "5.4"
diff --git a/pygost/gost3410.py b/pygost/gost3410.py
index f320c3f7ff82b58c7bfda7a539e9206d9fa94943ae51e8a2f2bbd4762312e7cb..2a079b70dc31a12b95280f63061cda8c7fcfccfe32679bc565b6e3e0838a40da 100644
--- a/pygost/gost3410.py
+++ b/pygost/gost3410.py
@@ -324,8 +324,24 @@     """Unmarshal little-endian private key
 
     :param bytes prv: serialized private key
     :rtype: long
+
+    It is advisable to use :py:func:`pygost.gost3410.prv_marshal` to
+    assure that key i in curve's Q field for better compatibility with
+    some implementations.
     """
     return bytes2long(prv[::-1])
+
+
+def prv_marshal(curve, prv):
+    """Marshal little-endian private key
+
+    :param GOST3410Curve curve: curve to use
+    :param long prv: serialized private key
+    :rtype: bytes
+
+    Key is in curve's Q field.
+    """
+    return long2bytes(prv % curve.q, point_size(prv))[::-1]
 
 
 def pub_marshal(pub):
diff --git a/pygost/stubs/pygost/gost3410.pyi b/pygost/stubs/pygost/gost3410.pyi
index a347458e7a75be2c9c0b6b015fd1e53fcc75dcd161d1bd9b414033e54d261228..3069a24a941c468411a0c6d5a08ff407f60ea84a1707c32c6255c21af445a720 100644
--- a/pygost/stubs/pygost/gost3410.pyi
+++ b/pygost/stubs/pygost/gost3410.pyi
@@ -55,6 +55,9 @@
 def prv_unmarshal(prv: bytes) -> int: ...
 
 
+def prv_marshal(curve: GOST3410Curve, prv: int) -> bytes: ...
+
+
 def pub_marshal(pub: PublicKey) -> bytes: ...
 
 
diff --git a/pygost/test_gost3410.py b/pygost/test_gost3410.py
index d000cd4624e32327d9daa8159ad6542ae0ac894518a8579af76bb5fbff716d34..a1a8f303cdae49a8e351f56730a6a41ae885439da9756a877faf5de4678c7218 100644
--- a/pygost/test_gost3410.py
+++ b/pygost/test_gost3410.py
@@ -19,6 +19,8 @@ from unittest import TestCase
 
 from pygost.gost3410 import CURVES
 from pygost.gost3410 import GOST3410Curve
+from pygost.gost3410 import prv_marshal
+from pygost.gost3410 import prv_unmarshal
 from pygost.gost3410 import public_key
 from pygost.gost3410 import sign
 from pygost.gost3410 import uv2xy
@@ -81,8 +83,8 @@         self.assertTrue(verify(c, (pubX, pubY), digest, signature))
 
     def test_sequence(self):
         c = CURVES["id-GostR3410-2001-TestParamSet"]
-        prv = bytes2long(urandom(32))
-        pubX, pubY = public_key(c, prv)
+        prv = prv_unmarshal(urandom(32))
+        pubX, pubY = public_key(c, prv_unmarshal(prv_marshal(c, prv)))
         for _ in range(20):
             digest = urandom(32)
             s = sign(c, prv, digest)
@@ -255,7 +257,7 @@
     def test_sequence(self):
         c = CURVES["id-tc26-gost-3410-12-512-paramSetA"]
         prv = bytes2long(urandom(64))
-        pubX, pubY = public_key(c, prv)
+        pubX, pubY = public_key(c, prv_unmarshal(prv_marshal(c, prv)))
         for _ in range(20):
             digest = urandom(64)
             s = sign(c, prv, digest)