diff --git a/composer.json b/composer.json
index ad50b25..fba70b8 100644
--- a/composer.json
+++ b/composer.json
@@ -29,11 +29,11 @@
         "php": ">=5.3.0",
         "evenement/evenement": "^3.0 || ^2.0 || ^1.0",
         "react/event-loop": "^1.2",
-        "react/stream": "^1.2"
+        "react/stream": "^1.4"
     },
     "require-dev": {
         "phpunit/phpunit": "^9.6 || ^5.7 || ^4.8.36",
-        "react/socket": "^1.8",
+        "react/socket": "^1.16",
         "sebastian/environment": "^5.0 || ^3.0 || ^2.0 || ^1.0"
     },
     "autoload": {
diff --git a/src/Process.php b/src/Process.php
index d947039..406e417 100644
--- a/src/Process.php
+++ b/src/Process.php
@@ -103,8 +103,14 @@ class Process extends EventEmitter
     * @param null|array  $fds File descriptors to allocate for this process (or null = default STDIO streams)
     * @throws \LogicException On windows or when proc_open() is not installed
     */
-    public function __construct($cmd, $cwd = null, array $env = null, array $fds = null)
+    public function __construct($cmd, $cwd = null, $env = null, $fds = null)
     {
+        if ($env !== null && !\is_array($env)) { // manual type check to support legacy PHP < 7.1
+            throw new \InvalidArgumentException('Argument #3 ($env) expected null|array');
+        }
+        if ($fds !== null && !\is_array($fds)) { // manual type check to support legacy PHP < 7.1
+            throw new \InvalidArgumentException('Argument #4 ($fds) expected null|array');
+        }
         if (!\function_exists('proc_open')) {
             throw new \LogicException('The Process class relies on proc_open(), which is not available on your PHP installation.');
         }
@@ -154,8 +160,11 @@ public function __construct($cmd, $cwd = null, array $env = null, array $fds = n
      * @param float          $interval    Interval to periodically monitor process state (seconds)
      * @throws \RuntimeException If the process is already running or fails to start
      */
-    public function start(LoopInterface $loop = null, $interval = 0.1)
+    public function start($loop = null, $interval = 0.1)
     {
+        if ($loop !== null && !$loop instanceof LoopInterface) { // manual type check to support legacy PHP < 7.1
+            throw new \InvalidArgumentException('Argument #1 ($loop) expected null|React\EventLoop\LoopInterface');
+        }
         if ($this->isRunning()) {
             throw new \RuntimeException('Process is already running');
         }
diff --git a/tests/AbstractProcessTest.php b/tests/AbstractProcessTest.php
index 606336f..4a81d0b 100644
--- a/tests/AbstractProcessTest.php
+++ b/tests/AbstractProcessTest.php
@@ -11,6 +11,18 @@ abstract class AbstractProcessTest extends TestCase
 {
     abstract public function createLoop();
 
+    public function testCtorThrowsForInvalidEnv()
+    {
+        $this->setExpectedException('InvalidArgumentException', 'Argument #3 ($env) expected null|array');
+        new Process('exit 0', null, 'env');
+    }
+
+    public function testCtorThrowsForInvalidFds()
+    {
+        $this->setExpectedException('InvalidArgumentException', 'Argument #4 ($fds) expected null|array');
+        new Process('exit 0', null, null, 'fds');
+    }
+
     public function testGetCommand()
     {
         $process = new Process('echo foo', null, null, array());
@@ -126,6 +138,14 @@ public function testStartWithCustomPipesWillAssignPipes()
         $this->assertInstanceOf('React\Stream\WritableStreamInterface', $process->pipes[3]);
     }
 
+    public function testStartWithInvalidLoopWillThrow()
+    {
+        $process = new Process('exit 0', null, null, array());
+
+        $this->setExpectedException('InvalidArgumentException', 'Argument #1 ($loop) expected null|React\EventLoop\LoopInterface');
+        $process->start('loop');
+    }
+
     public function testStartWithInvalidFileDescriptorPathWillThrowWithoutCallingCustomErrorHandler()
     {
         if (defined('HHVM_VERSION')) {