diff --git a/fsnotify.cabal b/fsnotify.cabal
index 8bc6581..042f090 100644
--- a/fsnotify.cabal
+++ b/fsnotify.cabal
@@ -49,13 +49,11 @@ library
     , unix-compat >=0.2
   default-language: Haskell2010
   if os(linux)
-    cpp-options: -DOS_Linux
+    cpp-options: -DOS_Linux -DHAVE_NATIVE_WATCHER
   if os(windows)
-    cpp-options: -DOS_Win32
+    cpp-options: -DOS_Win32 -DHAVE_NATIVE_WATCHER
   if os(darwin)
-    cpp-options: -DOS_Mac
-  if os(freebsd) || os(netbsd) || os(openbsd)
-    cpp-options: -DOS_BSD
+    cpp-options: -DOS_Mac -DHAVE_NATIVE_WATCHER
   if os(linux)
     other-modules:
         System.FSNotify.Linux
@@ -103,13 +101,11 @@ executable example
     , unliftio
   default-language: Haskell2010
   if os(linux)
-    cpp-options: -DOS_Linux
+    cpp-options: -DOS_Linux -DHAVE_NATIVE_WATCHER
   if os(windows)
-    cpp-options: -DOS_Win32
+    cpp-options: -DOS_Win32 -DHAVE_NATIVE_WATCHER
   if os(darwin)
-    cpp-options: -DOS_Mac
-  if os(freebsd) || os(netbsd) || os(openbsd)
-    cpp-options: -DOS_BSD
+    cpp-options: -DOS_Mac -DHAVE_NATIVE_WATCHER
 
 test-suite tests
   type: exitcode-stdio-1.0
@@ -140,13 +136,11 @@ test-suite tests
     , unliftio >=0.2.20
   default-language: Haskell2010
   if os(linux)
-    cpp-options: -DOS_Linux
+    cpp-options: -DOS_Linux -DHAVE_NATIVE_WATCHER
   if os(windows)
-    cpp-options: -DOS_Win32
+    cpp-options: -DOS_Win32 -DHAVE_NATIVE_WATCHER
   if os(darwin)
-    cpp-options: -DOS_Mac
-  if os(freebsd) || os(netbsd) || os(openbsd)
-    cpp-options: -DOS_BSD
+    cpp-options: -DOS_Mac -DHAVE_NATIVE_WATCHER
   if os(windows)
     build-depends:
         Win32
diff --git a/package.yaml b/package.yaml
index c1ad00a..d811d77 100644
--- a/package.yaml
+++ b/package.yaml
@@ -16,13 +16,11 @@ extra-source-files:
 
 when:
 - condition: os(linux)
-  cpp-options: -DOS_Linux
+  cpp-options: -DOS_Linux -DHAVE_NATIVE_WATCHER
 - condition: os(windows)
-  cpp-options: -DOS_Win32
+  cpp-options: -DOS_Win32 -DHAVE_NATIVE_WATCHER
 - condition: os(darwin)
-  cpp-options: -DOS_Mac
-- condition: os(freebsd) || os(netbsd) || os(openbsd)
-  cpp-options: -DOS_BSD
+  cpp-options: -DOS_Mac -DHAVE_NATIVE_WATCHER
 
 default-extensions:
 - ScopedTypeVariables
diff --git a/src/System/FSNotify.hs b/src/System/FSNotify.hs
index 6b61fd4..60a6a83 100644
--- a/src/System/FSNotify.hs
+++ b/src/System/FSNotify.hs
@@ -110,10 +110,10 @@ data WatchManager = forall manager argType. FileListener manager argType =>
 
 -- | Default configuration
 --
--- * Uses OS watch mode and single thread.
+-- * Uses OS watch mode (if possible) and single thread.
 defaultConfig :: WatchConfig
 defaultConfig = WatchConfig {
-#ifdef OS_BSD
+#ifndef HAVE_NATIVE_WATCHER
   confWatchMode = WatchModePoll 500000
 #else
   confWatchMode = WatchModeOS
@@ -163,12 +163,12 @@ startManagerConf conf = do
 
   case confWatchMode conf of
     WatchModePoll interval -> WatchManager conf <$> liftIO (createPollManager interval) <*> globalWatchChan
-#ifndef OS_BSD
+#ifdef HAVE_NATIVE_WATCHER
     WatchModeOS -> liftIO (initSession ()) >>= createManager
 #endif
 
   where
-#ifndef OS_BSD
+#ifdef HAVE_NATIVE_WATCHER
     createManager :: Either T.Text NativeManager -> IO WatchManager
     createManager (Right nativeManager) = WatchManager conf nativeManager <$> globalWatchChan
     createManager (Left err) = throwIO $ userError $ T.unpack $ "Error: couldn't start native file manager: " <> err
diff --git a/src/System/FSNotify/Types.hs b/src/System/FSNotify/Types.hs
index 48dc2a7..00b7ace 100644
--- a/src/System/FSNotify/Types.hs
+++ b/src/System/FSNotify/Types.hs
@@ -61,10 +61,10 @@ data WatchMode =
   }
   -- ^ Detect changes by polling the filesystem. Less efficient and may miss fast changes. Not recommended
   -- unless you're experiencing problems with 'WatchModeOS' (or 'WatchModeOS' is not supported on your platform).
-#ifndef OS_BSD
+#ifdef HAVE_NATIVE_WATCHER
   | WatchModeOS
   -- ^ Use OS-specific mechanisms to be notified of changes (inotify on Linux, FSEvents on OSX, etc.).
-  -- Not currently available on *BSD.
+  -- Not currently available on e.g. *BSD and WASI.
 #endif
 
 data ThreadingMode =
diff --git a/test/FSNotify/Test/EventTests.hs b/test/FSNotify/Test/EventTests.hs
index bfc2368..4497162 100644
--- a/test/FSNotify/Test/EventTests.hs
+++ b/test/FSNotify/Test/EventTests.hs
@@ -29,7 +29,7 @@ eventTests :: (
   MonadUnliftIO m, MonadThrow m
   ) => ThreadingMode -> SpecFree context m ()
 eventTests threadingMode = describe "Tests" $ parallelWithoutDirectory $ do
-  let pollOptions = if isBSD then [True] else [False, True]
+  let pollOptions = if haveNativeWatcher then [False, True] else [True]
 
   forM_ pollOptions $ \poll -> describe (if poll then "Polling" else "Native") $ parallelWithoutDirectory $ do
     forM_ [False, True] $ \recursive -> describe (if recursive then "Recursive" else "Non-recursive") $ parallelWithoutDirectory $
diff --git a/test/FSNotify/Test/Util.hs b/test/FSNotify/Test/Util.hs
index d0d392b..24e1b42 100644
--- a/test/FSNotify/Test/Util.hs
+++ b/test/FSNotify/Test/Util.hs
@@ -66,11 +66,11 @@ isLinux = True
 isLinux = False
 #endif
 
-isBSD :: Bool
-#ifdef OS_BSD
-isBSD = True
+haveNativeWatcher :: Bool
+#ifdef HAVE_NATIVE_WATCHER
+haveNativeWatcher = True
 #else
-isBSD = False
+haveNativeWatcher = False
 #endif
 
 waitUntil :: MonadUnliftIO m => Double -> m a -> m a
@@ -132,7 +132,7 @@ withTestFolder threadingMode poll recursive nested setup action = do
     when (isMac || poll) $ threadDelay (max 1000000 pollInterval)
 
     let conf = defaultConfig {
-#ifdef OS_BSD
+#ifndef HAVE_NATIVE_WATCHER
           confWatchMode = if poll then WatchModePoll pollInterval else error "No native watcher available."
 #else
           confWatchMode = if poll then WatchModePoll pollInterval else WatchModeOS