diff --git a/System/Win32/MinTTY.hsc b/System/Win32/MinTTY.hsc
--- a/System/Win32/MinTTY.hsc
+++ b/System/Win32/MinTTY.hsc
@@ -31,10 +31,9 @@
 #if MIN_VERSION_base(4,6,0)
 import Control.Exception (catch)
 #endif
-import Data.List (isPrefixOf, isInfixOf, isSuffixOf)
+import Data.List (isInfixOf)
 import Foreign
 import Foreign.C.Types
-import System.FilePath (takeFileName)
 
 #if __GLASGOW_HASKELL__ < 711
 #let alignment t = "%lu", (unsigned long)offsetof(struct {char x__; t (y__); }, y__)
@@ -91,11 +90,8 @@
     return False
 
 cygwinMSYSCheck :: String -> Bool
-cygwinMSYSCheck fn = ("cygwin-" `isPrefixOf` fn' || "msys-" `isPrefixOf` fn') &&
-            "-pty" `isInfixOf` fn' &&
-            "-master" `isSuffixOf` fn'
-  where
-    fn' = takeFileName fn
+cygwinMSYSCheck fn = ("cygwin-" `isInfixOf` fn || "msys-" `isInfixOf` fn) &&
+            "-pty" `isInfixOf` fn
 -- Note that GetFileInformationByHandleEx might return a filepath like:
 --
 --    \msys-dd50a72ab4668b33-pty1-to-master
@@ -105,8 +101,16 @@
 --    \Device\NamedPipe\msys-dd50a72ab4668b33-pty1-to-master
 --
 -- This means we can't rely on "\cygwin-" or "\msys-" being at the very start
--- of the filepath. Therefore, we must take care to first call takeFileName
--- before checking for "cygwin" or "msys" at the start using `isPrefixOf`.
+-- of the filepath. As a result, we use `isPrefixOf` to check for "cygwin" and
+-- "msys".
+--
+-- It's unclear if "-master" will always appear in the filepath name. Recent
+-- versions of MinTTY have been known to give filepaths like this (#186):
+--
+--    \msys-dd50a72ab4668b33-pty0-to-master-nat
+--
+-- Just in case MinTTY ever changes this convention, we don't bother checking
+-- for the presence of "-master" in the filepath name at all.
 
 getFileNameByHandle :: HANDLE -> IO String
 getFileNameByHandle h = do
diff --git a/Win32.cabal b/Win32.cabal
--- a/Win32.cabal
+++ b/Win32.cabal
@@ -1,5 +1,5 @@
 name:           Win32
-version:        2.13.0.0
+version:        2.13.1.0
 license:        BSD3
 license-file:   LICENSE
 author:         Alastair Reid, shelarcy, Tamar Christina
diff --git a/changelog.md b/changelog.md
--- a/changelog.md
+++ b/changelog.md
@@ -1,5 +1,11 @@
 # Changelog for [`Win32` package](http://hackage.haskell.org/package/Win32)
 
+## 2.13.1.0 November 2021
+
+* Fix a bug in which `System.Win32.MinTTY.isMinTTY` would incorrectly return
+  `False` on recent versions of MinTTY. (See #187)
+* Add all flags for CreateToolhelp32Snapshot.  (See #185)
+
 ## 2.13.0.0 August 2021
 
 * Fix type of c_SetWindowLongPtr. See #180
diff --git a/include/tlhelp32_compat.h b/include/tlhelp32_compat.h
--- a/include/tlhelp32_compat.h
+++ b/include/tlhelp32_compat.h
@@ -6,10 +6,21 @@
  */
 #if __GLASGOW_HASKELL__ > 708
 #else
-// Some declarations from tlhelp32.h that we need in Win32
+// Declarations from tlhelp32.h that Win32 requires
 #include <windows.h>
 
+// CreateToolhelp32Snapshot Flags
+// https://docs.microsoft.com/en-us/windows/win32/api/tlhelp32/nf-tlhelp32-createtoolhelp32snapshot
+
+#define TH32CS_INHERIT      0x80000000
+
+#define TH32CS_SNAPHEAPLIST 0x00000001
+#define TH32CS_SNAPPROCESS  0x00000002
+#define TH32CS_SNAPTHREAD   0x00000004
+#define TH32CS_SNAPMODULE   0x00000008
 #define TH32CS_SNAPMODULE32 0x00000010
+
+#define TH32CS_SNAPALL (TH32CS_SNAPHEAPLIST|TH32CS_SNAPPROCESS|TH32CS_SNAPTHREAD|TH32CS_SNAPMODULE)
 
 #endif
 #endif /* TLHELP32_COMPAT_H */