diff --git a/spec/StreamFactory/StreamFactoryBehavior.php b/spec/StreamFactory/StreamFactoryBehavior.php
index afc67ef..f78a1c6 100644
--- a/spec/StreamFactory/StreamFactoryBehavior.php
+++ b/spec/StreamFactory/StreamFactoryBehavior.php
@@ -2,6 +2,9 @@
 
 namespace spec\Http\Message\StreamFactory;
 
+use GuzzleHttp\Psr7\Stream;
+use Psr\Http\Message\StreamInterface;
+
 trait StreamFactoryBehavior
 {
     function it_is_a_stream_factory()
@@ -32,4 +35,33 @@ function it_creates_a_stream_from_non_seekable_resource()
         $this->createStream($resource)
             ->shouldHaveType('Psr\Http\Message\StreamInterface');
     }
+
+    function it_does_not_rewind_existing_stream()
+    {
+        $stream = new Stream(fopen('php://memory', 'rw'));
+        $stream->write('abcdef');
+        $stream->seek(3);
+
+        $this->createStream($stream)
+            ->shouldHaveContent('def');
+    }
+
+    function it_does_not_rewind_existing_resource()
+    {
+        $resource = fopen('php://memory', 'rw');
+        fwrite($resource, 'abcdef');
+        fseek($resource, 3);
+
+        $this->createStream($resource)
+            ->shouldHaveContent('def');
+    }
+
+    public function getMatchers()
+    {
+        return [
+            'haveContent' => function (StreamInterface $subject, $key) {
+                return $subject->getContents() === $key;
+            },
+        ];
+    }
 }
diff --git a/src/StreamFactory/DiactorosStreamFactory.php b/src/StreamFactory/DiactorosStreamFactory.php
index a73abb0..a75ec98 100644
--- a/src/StreamFactory/DiactorosStreamFactory.php
+++ b/src/StreamFactory/DiactorosStreamFactory.php
@@ -18,26 +18,19 @@ final class DiactorosStreamFactory implements StreamFactory
      */
     public function createStream($body = null)
     {
-        if (!$body instanceof StreamInterface) {
-            if (is_resource($body)) {
-                $body = new Stream($body);
-            } else {
-                $stream = new Stream('php://memory', 'rw');
-
-                if (null === $body || '' === $body) {
-                    return $stream;
-                }
-
-                $stream->write((string) $body);
+        if ($body instanceof StreamInterface) {
+            return $body;
+        }
 
-                $body = $stream;
-            }
+        if (is_resource($body)) {
+            return new Stream($body);
         }
 
-        if ($body->isSeekable()) {
-            $body->rewind();
+        $stream = new Stream('php://memory', 'rw');
+        if (null !== $body && '' !== $body) {
+            $stream->write((string) $body);
         }
 
-        return $body;
+        return $stream;
     }
 }
diff --git a/src/StreamFactory/SlimStreamFactory.php b/src/StreamFactory/SlimStreamFactory.php
index ba0bb17..efcadc4 100644
--- a/src/StreamFactory/SlimStreamFactory.php
+++ b/src/StreamFactory/SlimStreamFactory.php
@@ -23,20 +23,13 @@ public function createStream($body = null)
         }
 
         if (is_resource($body)) {
-            $stream = new Stream($body);
-        } else {
-            $resource = fopen('php://memory', 'r+');
-            $stream = new Stream($resource);
-
-            if (null === $body || '' === $body) {
-                return $stream;
-            }
-
-            $stream->write((string) $body);
+            return new Stream($body);
         }
 
-        if ($stream->isSeekable()) {
-            $stream->rewind();
+        $resource = fopen('php://memory', 'r+');
+        $stream = new Stream($resource);
+        if (null !== $body && '' !== $body) {
+            $stream->write((string) $body);
         }
 
         return $stream;