diff --git a/src/borg/platform/__init__.py b/src/borg/platform/__init__.py
index 06ff8e42a..f2f5e4fe2 100644
--- a/src/borg/platform/__init__.py
+++ b/src/borg/platform/__init__.py
@@ -4,7 +4,7 @@ Platform-specific APIs.
 Public APIs are documented in platform.base.
 """
 
-from ..platformflags import is_win32, is_linux, is_freebsd, is_darwin
+from ..platformflags import is_win32, is_linux, is_freebsd, is_darwin, is_cygwin
 
 from .base import ENOATTR, API_VERSION
 from .base import SaveFile, sync_dir, fdatasync, safe_fadvise
diff --git a/src/borg/platformflags.py b/src/borg/platformflags.py
index 64525b8aa..a4dd6d6e3 100644
--- a/src/borg/platformflags.py
+++ b/src/borg/platformflags.py
@@ -7,6 +7,8 @@ Use these Flags instead of sys.platform.startswith('<OS>') or try/except.
 import sys
 
 is_win32 = sys.platform.startswith("win32")
+is_cygwin = sys.platform.startswith("cygwin")
+
 is_linux = sys.platform.startswith("linux")
 is_freebsd = sys.platform.startswith("freebsd")
 is_darwin = sys.platform.startswith("darwin")
diff --git a/src/borg/testsuite/helpers.py b/src/borg/testsuite/helpers.py
index 7bb9f814f..6e2039412 100644
--- a/src/borg/testsuite/helpers.py
+++ b/src/borg/testsuite/helpers.py
@@ -42,6 +42,7 @@ from ..helpers import iter_separated
 from ..helpers import eval_escapes
 from ..helpers import safe_unlink
 from ..helpers.passphrase import Passphrase, PasswordRetriesExceeded
+from ..platform import is_cygwin
 
 from . import BaseTestCase, FakeInputs
 
@@ -596,6 +597,7 @@ def test_parse_file_size_invalid(string):
         parse_file_size(string)
 
 
+@pytest.mark.skipif(is_cygwin, reason="ignore slow msgpack on cygwin")
 def test_is_slow_msgpack():
     # we need to import upstream msgpack package here, not helpers.msgpack:
     import msgpack