VERSION         |  2 +-
 doc/install.rst | 12 ++++++------
 doc/news.rst    |  8 ++++++++
 doc/thanks.rst  |  2 ++
 pyderasn.py     | 17 ++++++++++-------

diff --git a/VERSION b/VERSION
index 0ff4c879ffc21ccff360dbb4e55627d804ff95ab0735552cd4dab6ba75d57c45..1ef68e351036fb994c26bcfc348dbcadef5b77c652b03d1048ee3381eb92c4db 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-8.0
+8.1
diff --git a/doc/install.rst b/doc/install.rst
index fe578969053ad77c1fd7ef7b7f3b6fc02d9a9d4aaf00be2b98b99b307437f413..5714645e77918d55c58fce7d7389d9a460851b22508e1d84303fd019fdd9725f 100644
--- a/doc/install.rst
+++ b/doc/install.rst
@@ -4,11 +4,11 @@
 Preferable way is to :ref:`download <download>` tarball with the
 signature from `official website <http://pyderasn.cypherpunks.ru/>`__::
 
-    $ [fetch|wget] http://pyderasn.cypherpunks.ru/pyderasn-8.0.tar.xz
-    $ [fetch|wget] http://pyderasn.cypherpunks.ru/pyderasn-8.0.tar.xz.sig
-    $ gpg --verify pyderasn-8.0.tar.xz.sig pyderasn-8.0.tar.xz
-    $ xz --decompress --stdout pyderasn-8.0.tar.xz | tar xf -
-    $ cd pyderasn-8.0
+    $ [fetch|wget] http://pyderasn.cypherpunks.ru/pyderasn-8.1.tar.xz
+    $ [fetch|wget] http://pyderasn.cypherpunks.ru/pyderasn-8.1.tar.xz.sig
+    $ gpg --verify pyderasn-8.1.tar.xz.sig pyderasn-8.1.tar.xz
+    $ xz --decompress --stdout pyderasn-8.1.tar.xz | tar xf -
+    $ cd pyderasn-8.1
     $ python setup.py install
     # or copy pyderasn.py (+six.py, possibly termcolor.py) to your PYTHONPATH
 
@@ -21,7 +21,7 @@
 You could use pip (**no** OpenPGP authentication is performed!) with PyPI::
 
     $ cat > requirements.txt <<EOF
-    pyderasn==8.0 --hash=sha256:TO-BE-FILLED
+    pyderasn==8.1 --hash=sha256:TO-BE-FILLED
     six==1.14.0 --hash=sha256:236bdbdce46e6e6a3d61a337c0f8b763ca1e8717c03b369e87a7ec7ce1319c0a
     EOF
     $ pip install --requirement requirements.txt
diff --git a/doc/news.rst b/doc/news.rst
index 2ff4e6b17eca036c2d2177e78091138640ef58a8c53bd4e92621f63c8ff7eff6..b0725c86194b18226623412ae6ecdda9d0cb370f03c3d3d6db8038c558435780 100644
--- a/doc/news.rst
+++ b/doc/news.rst
@@ -1,6 +1,14 @@
 News
 ====
 
+.. _release8.1:
+
+8.1
+---
+* Workability under Microsoft Windows OS should be restored: it has
+  different ``mmap`` constants and implementation, preventing
+  ``pyderasn`` importing
+
 .. _release8.0:
 
 8.0
diff --git a/doc/thanks.rst b/doc/thanks.rst
index d3b1d99a916dabc80d3b1d46bd0a51388fd12002c6a096dfb5f740c3f165dfab..bba1705a83400c350e2c2cc9c271a0885e2748bb2820746590ed658eae1e56f7 100644
--- a/doc/thanks.rst
+++ b/doc/thanks.rst
@@ -7,3 +7,5 @@ * `Nikolay Ivanov <gmail@nekolyanich.com>`_ for helping with
   :py:class:`pyderasn.AutoAddSlots` metaclass
 * `Tim Perevezentsev <riffm2005@gmail.com>`_ for huge quantity of
   improvement ideas
+* `Evgeny Drobotun <drobotun@xakep.ru>`_ for testing under Windows
+  and bugreporting
diff --git a/pyderasn.py b/pyderasn.py
index 0a110171386be4aa2aff412062b9d97713cdd4c39f16989017d28422c32b7b10..32fefcb2fcdc174ca8213c69798f837f26054b8cef68faa1b68ace18afb61417 100755
--- a/pyderasn.py
+++ b/pyderasn.py
@@ -1170,8 +1170,6 @@ from datetime import datetime
 from datetime import timedelta
 from io import BytesIO
 from math import ceil
-from mmap import mmap
-from mmap import PROT_READ
 from operator import attrgetter
 from string import ascii_letters
 from string import digits
@@ -1201,7 +1199,7 @@ except ImportError:  # pragma: no cover
     def colored(what, *args, **kwargs):
         return what
 
-__version__ = "8.0"
+__version__ = "8.1"
 
 __all__ = (
     "agg_octet_string",
@@ -1292,8 +1290,13 @@     """Make mmap-ed memoryview for reading from file
 
     :param fd: file object
     :returns: memoryview over read-only mmap-ing of the whole file
+
+    .. warning::
+
+       It is known to work under neither Python 2.x nor Windows.
     """
-    return memoryview(mmap(fd.fileno(), 0, prot=PROT_READ))
+    import mmap
+    return memoryview(mmap.mmap(fd.fileno(), length=0, prot=mmap.PROT_READ))
 
 
 def pureint(value):
@@ -7897,12 +7900,12 @@         type=argparse.FileType("rb"),
         help="Path to BER/CER/DER file you want to decode",
     )
     args = parser.parse_args()
-    if PY2:
+    try:
+        raw = file_mmaped(args.RAWFile)[args.skip:]
+    except:
         args.RAWFile.seek(args.skip)
         raw = memoryview(args.RAWFile.read())
         args.RAWFile.close()
-    else:
-        raw = file_mmaped(args.RAWFile)[args.skip:]
     oid_maps = (
         [obj_by_path(_path) for _path in (args.oids or "").split(",")]
         if args.oids else ()