diff --git a/README.md b/README.md
index 34dd8a9..234dfea 100644
--- a/README.md
+++ b/README.md
@@ -8,3 +8,6 @@ Differences with the V standard library `net` module:
 * Supports any kind of sockets, socket options, address families and protocols.
 
 The `netio.protocol` submodule provides access to the operatins system protocols database.
+
+`netio` is tested only on Linux, but should work on all POSIX-compliant operating systems.
+Microfost Windows support is not planned yet.