diff --git a/composer.json b/composer.json
index 7962557..0147b1d 100644
--- a/composer.json
+++ b/composer.json
@@ -16,6 +16,9 @@
     ],
     "prefer-stable": true,
     "minimum-stability": "dev",
+    "config": {
+        "secure-http": true
+    },
     "require": {
         "php": "^7.1",
         "ext-curl": "*",
@@ -30,7 +33,8 @@
         "guzzlehttp/psr7": "^1.0",
         "php-http/client-integration-tests": "^2.0",
         "phpunit/phpunit": "^7.5",
-        "zendframework/zend-diactoros": "^2.0"
+        "zendframework/zend-diactoros": "^2.0",
+        "donatj/mock-webserver": "^2.0"
     },
     "autoload": {
         "psr-4": {
diff --git a/phpunit.xml.dist b/phpunit.xml.dist
index 3f3b615..2c9938e 100644
--- a/phpunit.xml.dist
+++ b/phpunit.xml.dist
@@ -23,6 +23,10 @@
             <directory>tests/Unit</directory>
         </testsuite>
 
+        <testsuite name="Integration">
+            <directory>tests/Integration</directory>
+        </testsuite>
+
         <testsuite name="Functional">
             <directory>tests/Functional</directory>
             <!-- Exclude till https://github.com/php-http/message/issues/105 resolved. -->
diff --git a/src/MultiRunner.php b/src/MultiRunner.php
index 7a2c50c..d56cb28 100644
--- a/src/MultiRunner.php
+++ b/src/MultiRunner.php
@@ -14,6 +14,11 @@
  */
 class MultiRunner
 {
+    /**
+     * Timeout for curl_multi_select in seconds.
+     */
+    private const SELECT_TIMEOUT = 0.1;
+
     /**
      * cURL multi handle.
      *
@@ -84,18 +89,27 @@ public function remove(PromiseCore $core): void
     public function wait(PromiseCore $targetCore = null): void
     {
         do {
-            $status = curl_multi_exec($this->multiHandle, $active);
+            if (curl_multi_select($this->multiHandle, self::SELECT_TIMEOUT) === -1) {
+                // See https://bugs.php.net/bug.php?id=61141
+                usleep(250);
+            }
+
+            do {
+                $status = curl_multi_exec($this->multiHandle, $active);
+                // TODO CURLM_CALL_MULTI_PERFORM never returned since cURL 7.20.
+            } while ($status === CURLM_CALL_MULTI_PERFORM);
+
             $info = curl_multi_info_read($this->multiHandle);
-            if (false !== $info) {
+            if ($info !== false) {
                 $core = $this->findCoreByHandle($info['handle']);
 
-                if (null === $core) {
+                if ($core === null) {
                     // We have no promise for this handle. Drop it.
                     curl_multi_remove_handle($this->multiHandle, $info['handle']);
                     continue;
                 }
 
-                if (CURLE_OK === $info['result']) {
+                if ($info['result'] === CURLM_OK) {
                     $core->fulfill();
                 } else {
                     $error = curl_error($core->getHandle());
@@ -108,7 +122,7 @@ public function wait(PromiseCore $targetCore = null): void
                     return;
                 }
             }
-        } while ($status === CURLM_CALL_MULTI_PERFORM || $active);
+        } while ($active);
     }
 
     /**
diff --git a/tests/Integration/MultiRunnerTest.php b/tests/Integration/MultiRunnerTest.php
new file mode 100644
index 0000000..b0d554f
--- /dev/null
+++ b/tests/Integration/MultiRunnerTest.php
@@ -0,0 +1,91 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Http\Client\Curl\Tests\Integration;
+
+use donatj\MockWebServer\MockWebServer;
+use Http\Client\Curl\MultiRunner;
+use Http\Client\Curl\PromiseCore;
+use PHPUnit\Framework\TestCase;
+
+/**
+ * Tests for Http\Client\Curl\MultiRunner.
+ *
+ * @covers \Http\Client\Curl\MultiRunner
+ */
+class MultiRunnerTest extends TestCase
+{
+    /**
+     * Test HTTP server.
+     *
+     * @var MockWebServer
+     */
+    private static $server;
+
+    /**
+     * Prepare environment for all tests.
+     */
+    public static function setUpBeforeClass(): void
+    {
+        parent::setUpBeforeClass();
+
+        self::$server = new MockWebServer();
+        self::$server->start();
+    }
+
+    /**
+     * Cleanup environment after all tests.
+     */
+    public static function tearDownAfterClass(): void
+    {
+        self::$server->stop();
+
+        parent::tearDownAfterClass();
+    }
+
+    public function testWait(): void
+    {
+        $runner = new MultiRunner();
+
+        $handle = $this->createCurlHandle('/');
+        $core1 = $this->createConfiguredMock(PromiseCore::class, ['getHandle' => $handle]);
+        $core1
+            ->expects(self::once())
+            ->method('fulfill');
+
+        $handle = $this->createCurlHandle('/');
+        $core2 = $this->createConfiguredMock(PromiseCore::class, ['getHandle' => $handle]);
+        $core2
+            ->expects(self::once())
+            ->method('fulfill');
+
+        $runner->add($core1);
+        $runner->add($core2);
+
+        $runner->wait($core1);
+        $runner->wait($core2);
+    }
+
+    /**
+     * Create cURL handle with given parameters.
+     *
+     * @param string $url Request URL relative to server root.
+     *
+     * @return resource
+     */
+    private function createCurlHandle(string $url)
+    {
+        $handle = curl_init();
+        self::assertNotFalse($handle);
+
+        curl_setopt_array(
+            $handle,
+            [
+                CURLOPT_URL => self::$server->getServerRoot() . $url
+            ]
+        );
+
+        return $handle;
+    }
+}