diff --git a/src/Stream.php b/src/Stream.php
index 73d24f43..d9e7409c 100644
--- a/src/Stream.php
+++ b/src/Stream.php
@@ -10,6 +10,17 @@
  */
 class Stream implements StreamInterface
 {
+    /**
+     * Resource modes.
+     *
+     * @var string
+     *
+     * @see http://php.net/manual/function.fopen.php
+     * @see http://php.net/manual/en/function.gzopen.php
+     */
+    const READABLE_MODES = '/r|a\+|ab\+|w\+|wb\+|x\+|xb\+|c\+|cb\+/';
+    const WRITABLE_MODES = '/a|w|r\+|rb\+|rw|x|c/';
+
     private $stream;
     private $size;
     private $seekable;
@@ -18,22 +29,6 @@ class Stream implements StreamInterface
     private $uri;
     private $customMetadata;
 
-    /** @var array Hash of readable and writable stream types */
-    private static $readWriteHash = [
-        'read' => [
-            'r' => true, 'w+' => true, 'r+' => true, 'x+' => true, 'c+' => true,
-            'rb' => true, 'w+b' => true, 'r+b' => true, 'x+b' => true,
-            'c+b' => true, 'rt' => true, 'w+t' => true, 'r+t' => true,
-            'x+t' => true, 'c+t' => true, 'a+' => true, 'rb+' => true,
-        ],
-        'write' => [
-            'w' => true, 'w+' => true, 'rw' => true, 'r+' => true, 'x+' => true,
-            'c+' => true, 'wb' => true, 'w+b' => true, 'r+b' => true, 'rb+' => true,
-            'x+b' => true, 'c+b' => true, 'w+t' => true, 'r+t' => true,
-            'x+t' => true, 'c+t' => true, 'a' => true, 'a+' => true
-        ]
-    ];
-
     /**
      * This constructor accepts an associative array of options.
      *
@@ -65,8 +60,8 @@ public function __construct($stream, $options = [])
         $this->stream = $stream;
         $meta = stream_get_meta_data($this->stream);
         $this->seekable = $meta['seekable'];
-        $this->readable = isset(self::$readWriteHash['read'][$meta['mode']]);
-        $this->writable = isset(self::$readWriteHash['write'][$meta['mode']]);
+        $this->readable = (bool)preg_match(self::READABLE_MODES, $meta['mode']);
+        $this->writable = (bool)preg_match(self::WRITABLE_MODES, $meta['mode']);
         $this->uri = $this->getMetadata('uri');
     }
 
diff --git a/tests/StreamTest.php b/tests/StreamTest.php
index bf4653c0..63421ce5 100644
--- a/tests/StreamTest.php
+++ b/tests/StreamTest.php
@@ -231,6 +231,133 @@ public function testStreamReadingFreadError()
         self::$isFReadError = false;
         $stream->close();
     }
+
+    /**
+     * @dataProvider gzipModeProvider
+     *
+     * @param string $mode
+     * @param bool   $readable
+     * @param bool   $writable
+     */
+    public function testGzipStreamModes($mode, $readable, $writable)
+    {
+        if (defined('HHVM_VERSION')) {
+            $this->markTestSkipped('This does not work on HHVM.');
+        }
+
+        $r = gzopen('php://temp', $mode);
+        $stream = new Stream($r);
+
+        $this->assertSame($readable, $stream->isReadable());
+        $this->assertSame($writable, $stream->isWritable());
+
+        $stream->close();
+    }
+
+    public function gzipModeProvider()
+    {
+        return [
+            ['mode' => 'rb9', 'readable' => true, 'writable' => false],
+            ['mode' => 'wb2', 'readable' => false, 'writable' => true],
+        ];
+    }
+
+    /**
+     * @dataProvider readableModeProvider
+     *
+     * @param string $mode
+     */
+    public function testReadableStream($mode)
+    {
+        $r = fopen('php://temp', $mode);
+        $stream = new Stream($r);
+
+        $this->assertTrue($stream->isReadable());
+
+        $stream->close();
+    }
+
+    public function readableModeProvider()
+    {
+        return [
+            ['r'],
+            ['w+'],
+            ['r+'],
+            ['x+'],
+            ['c+'],
+            ['rb'],
+            ['w+b'],
+            ['r+b'],
+            ['x+b'],
+            ['c+b'],
+            ['rt'],
+            ['w+t'],
+            ['r+t'],
+            ['x+t'],
+            ['c+t'],
+            ['a+'],
+            ['rb+'],
+        ];
+    }
+
+    public function testWriteOnlyStreamIsNotReadable()
+    {
+        $r = fopen('php://output', 'w');
+        $stream = new Stream($r);
+
+        $this->assertFalse($stream->isReadable());
+
+        $stream->close();
+    }
+
+    /**
+     * @dataProvider writableModeProvider
+     *
+     * @param string $mode
+     */
+    public function testWritableStream($mode)
+    {
+        $r = fopen('php://temp', $mode);
+        $stream = new Stream($r);
+
+        $this->assertTrue($stream->isWritable());
+
+        $stream->close();
+    }
+
+    public function writableModeProvider()
+    {
+        return [
+            ['w'],
+            ['w+'],
+            ['rw'],
+            ['r+'],
+            ['x+'],
+            ['c+'],
+            ['wb'],
+            ['w+b'],
+            ['r+b'],
+            ['rb+'],
+            ['x+b'],
+            ['c+b'],
+            ['w+t'],
+            ['r+t'],
+            ['x+t'],
+            ['c+t'],
+            ['a'],
+            ['a+'],
+        ];
+    }
+
+    public function testReadOnlyStreamIsNotWritable()
+    {
+        $r = fopen('php://input', 'r');
+        $stream = new Stream($r);
+
+        $this->assertFalse($stream->isWritable());
+
+        $stream->close();
+    }
 }
 
 namespace GuzzleHttp\Psr7;