diff --git a/lib/Internal/Posix/Handle.php b/lib/Internal/Posix/Handle.php
index c1da8a4..134b465 100644
--- a/lib/Internal/Posix/Handle.php
+++ b/lib/Internal/Posix/Handle.php
@@ -5,6 +5,7 @@ namespace Amp\Process\Internal\Posix;
 use Amp\Deferred;
 use Amp\Process\Internal\ProcessHandle;
 
+/** @internal */
 final class Handle extends ProcessHandle {
     public function __construct() {
         $this->pidDeferred = new Deferred;
diff --git a/lib/Internal/Posix/Runner.php b/lib/Internal/Posix/Runner.php
index e2585e5..030940c 100644
--- a/lib/Internal/Posix/Runner.php
+++ b/lib/Internal/Posix/Runner.php
@@ -14,6 +14,7 @@ use Amp\Process\ProcessInputStream;
 use Amp\Process\ProcessOutputStream;
 use Amp\Promise;
 
+/** @internal */
 final class Runner implements ProcessRunner {
     const FD_SPEC = [
         ["pipe", "r"], // stdin
diff --git a/lib/Internal/Windows/Handle.php b/lib/Internal/Windows/Handle.php
index 99f034d..be34e36 100644
--- a/lib/Internal/Windows/Handle.php
+++ b/lib/Internal/Windows/Handle.php
@@ -5,6 +5,10 @@ namespace Amp\Process\Internal\Windows;
 use Amp\Deferred;
 use Amp\Process\Internal\ProcessHandle;
 
+/**
+ * @internal
+ * @codeCoverageIgnore Windows only.
+ */
 final class Handle extends ProcessHandle {
     public function __construct() {
         $this->joinDeferred = new Deferred;
diff --git a/lib/Internal/Windows/HandshakeStatus.php b/lib/Internal/Windows/HandshakeStatus.php
index e240af9..16734ad 100644
--- a/lib/Internal/Windows/HandshakeStatus.php
+++ b/lib/Internal/Windows/HandshakeStatus.php
@@ -2,6 +2,10 @@
 
 namespace Amp\Process\Internal\Windows;
 
+/**
+ * @internal
+ * @codeCoverageIgnore Windows only.
+ */
 final class HandshakeStatus {
     const SUCCESS = 0;
     const SIGNAL_UNEXPECTED = 0x01;
diff --git a/lib/Internal/Windows/PendingSocketClient.php b/lib/Internal/Windows/PendingSocketClient.php
index 866b3f5..bb21a4e 100644
--- a/lib/Internal/Windows/PendingSocketClient.php
+++ b/lib/Internal/Windows/PendingSocketClient.php
@@ -4,6 +4,10 @@ namespace Amp\Process\Internal\Windows;
 
 use Amp\Struct;
 
+/**
+ * @internal
+ * @codeCoverageIgnore Windows only.
+ */
 final class PendingSocketClient {
     use Struct;
 
diff --git a/lib/Internal/Windows/Runner.php b/lib/Internal/Windows/Runner.php
index c15f5c6..16b8447 100644
--- a/lib/Internal/Windows/Runner.php
+++ b/lib/Internal/Windows/Runner.php
@@ -13,6 +13,10 @@ use Amp\Process\ProcessOutputStream;
 use Amp\Promise;
 use const Amp\Process\BIN_DIR;
 
+/**
+ * @internal
+ * @codeCoverageIgnore Windows only.
+ */
 final class Runner implements ProcessRunner {
     const FD_SPEC = [
         ["pipe", "r"], // stdin
diff --git a/lib/Internal/Windows/SignalCode.php b/lib/Internal/Windows/SignalCode.php
index e0cc736..ce065f2 100644
--- a/lib/Internal/Windows/SignalCode.php
+++ b/lib/Internal/Windows/SignalCode.php
@@ -2,6 +2,10 @@
 
 namespace Amp\Process\Internal\Windows;
 
+/**
+ * @internal
+ * @codeCoverageIgnore Windows only.
+ */
 final class SignalCode {
     const HANDSHAKE = 0x01;
     const HANDSHAKE_ACK = 0x02;
diff --git a/lib/Internal/Windows/SocketConnector.php b/lib/Internal/Windows/SocketConnector.php
index 3149a21..02b03ac 100644
--- a/lib/Internal/Windows/SocketConnector.php
+++ b/lib/Internal/Windows/SocketConnector.php
@@ -8,6 +8,10 @@ use Amp\Loop;
 use Amp\Process\Internal\ProcessStatus;
 use Amp\Process\ProcessException;
 
+/**
+ * @internal
+ * @codeCoverageIgnore Windows only.
+ */
 final class SocketConnector {
     const SERVER_SOCKET_URI = 'tcp://127.0.0.1:0';
     const SECURITY_TOKEN_SIZE = 16;