diff --git a/src/Stream/Stream.php b/src/Stream/Stream.php
index 0b9e3fa..b0c901c 100644
--- a/src/Stream/Stream.php
+++ b/src/Stream/Stream.php
@@ -68,7 +68,8 @@ class Stream implements StreamableInterface
      */
     public function getSize()
     {
-        return null;
+        $statistics = fstat($this->handle);
+        return $statistics["size"] ?: null;
     }
 
     /**
diff --git a/test/tests/unit/Stream/StreamStreamTest.php b/test/tests/unit/Stream/StreamTest.php
similarity index 98%
rename from test/tests/unit/Stream/StreamStreamTest.php
rename to test/tests/unit/Stream/StreamTest.php
index f3bea4a..014f499 100644
--- a/test/tests/unit/Stream/StreamStreamTest.php
+++ b/test/tests/unit/Stream/StreamTest.php
@@ -108,10 +108,10 @@ class StreamTest extends \PHPUnit_Framework_TestCase
      * @covers WellRESTed\Stream\Stream::getSize
      * @uses WellRESTed\Stream\Stream
      */
-    public function testReturnsNullForSize()
+    public function testReturnsSize()
     {
         $stream = new Stream($this->handle);
-        $this->assertNull($stream->getSize());
+        $this->assertEquals(strlen($this->content), $stream->getSize());
     }
 
     /**