diff --git a/lib/functions.php b/lib/functions.php
index c88fea5..3aceb5a 100644
--- a/lib/functions.php
+++ b/lib/functions.php
@@ -5,30 +5,32 @@ namespace Amp\Process;
 const BIN_DIR = __DIR__ . DIRECTORY_SEPARATOR . '..' . DIRECTORY_SEPARATOR . 'bin';
 const IS_WINDOWS = (PHP_OS & "\xDF\xDF\xDF") === 'WIN';
 
-if (IS_WINDOWS) {
-    /**
-     * Escapes the command argument for safe inclusion into a Windows command string.
-     *
-     * @param string $arg
-     *
-     * @return string
-     */
-    function escapeArguments(string $arg): string
-    {
-        return '"' . \preg_replace_callback('(\\\\*("|$))', function (array $m): string {
-            return \str_repeat('\\', \strlen($m[0])) . $m[0];
-        }, $arg) . '"';
-    }
-} else {
-    /**
-     * Escapes the command argument for safe inclusion into a Posix shell command string.
-     *
-     * @param string $arg
-     *
-     * @return string
-     */
-    function escapeArguments(string $arg): string
-    {
-        return \escapeshellarg($arg);
+if (!\function_exists(__NAMESPACE__ . '\\escapeArguments')) {
+    if (IS_WINDOWS) {
+        /**
+         * Escapes the command argument for safe inclusion into a Windows command string.
+         *
+         * @param string $arg
+         *
+         * @return string
+         */
+        function escapeArguments(string $arg): string
+        {
+            return '"'.\preg_replace_callback('(\\\\*("|$))', function (array $m): string {
+                    return \str_repeat('\\', \strlen($m[0])).$m[0];
+                }, $arg).'"';
+        }
+    } else {
+        /**
+         * Escapes the command argument for safe inclusion into a Posix shell command string.
+         *
+         * @param string $arg
+         *
+         * @return string
+         */
+        function escapeArguments(string $arg): string
+        {
+            return \escapeshellarg($arg);
+        }
     }
 }