diff --git a/src/Message/Stream.php b/src/Message/Stream.php
index a37df74..4543e38 100644
--- a/src/Message/Stream.php
+++ b/src/Message/Stream.php
@@ -6,7 +6,10 @@ use Psr\Http\Message\StreamInterface;
 
 class Stream implements StreamInterface
 {
-    /** @var resource */
+    private const READABLE_MODES = ['r', 'r+', 'w+', 'a+', 'x+', 'c+'];
+    private const WRITABLE_MODES = ['r+', 'w', 'w+', 'a', 'a+', 'x', 'x+', 'c', 'c+'];
+
+    /** @var resource|null */
     private $resource;
 
     /**
@@ -46,18 +49,16 @@ class Stream implements StreamInterface
      */
     public function __toString()
     {
-        $string = "";
         try {
             if ($this->isSeekable()) {
-                rewind($this->resource);
+                $this->rewind();
             }
-            $string = $this->getContents();
-            // @codeCoverageIgnoreStart
+            return $this->getContents();
         } catch (\Exception $e) {
-            // @codeCoverageIgnoreEnd
-            // Silence exceptions in order to conform with PHP's string casting operations.
+            // Silence exceptions in order to conform with PHP's string casting
+            // operations.
+            return '';
         }
-        return $string;
     }
 
     /**
@@ -67,6 +68,10 @@ class Stream implements StreamInterface
      */
     public function close()
     {
+        if ($this->resource === null) {
+            return;
+        }
+
         $resource = $this->resource;
         fclose($resource);
         $this->resource = null;
@@ -93,6 +98,10 @@ class Stream implements StreamInterface
      */
     public function getSize()
     {
+        if ($this->resource === null) {
+            return null;
+        }
+
         $statistics = fstat($this->resource);
         if ($statistics && $statistics["size"]) {
             return $statistics["size"];
@@ -108,6 +117,10 @@ class Stream implements StreamInterface
      */
     public function tell()
     {
+        if ($this->resource === null) {
+            throw new \RuntimeException("Unable to retrieve current position of detached stream.");
+        }
+
         $position = ftell($this->resource);
         if ($position === false) {
             throw new \RuntimeException("Unable to retrieve current position of file pointer.");
@@ -122,6 +135,10 @@ class Stream implements StreamInterface
      */
     public function eof()
     {
+        if ($this->resource === null) {
+            return true;
+        }
+
         return feof($this->resource);
     }
 
@@ -132,6 +149,10 @@ class Stream implements StreamInterface
      */
     public function isSeekable()
     {
+        if ($this->resource === null) {
+            return false;
+        }
+
         return $this->getMetadata("seekable") == 1;
     }
 
@@ -149,6 +170,10 @@ class Stream implements StreamInterface
      */
     public function seek($offset, $whence = SEEK_SET)
     {
+        if ($this->resource === null) {
+            throw new \RuntimeException("Unable to seek detached stream.");
+        }
+
         $result = -1;
         if ($this->isSeekable()) {
             $result = fseek($this->resource, $offset, $whence);
@@ -170,12 +195,16 @@ class Stream implements StreamInterface
      */
     public function rewind()
     {
+        if ($this->resource === null) {
+            throw new \RuntimeException("Unable to seek detached stream.");
+        }
+
         $result = false;
         if ($this->isSeekable()) {
             $result = rewind($this->resource);
         }
         if ($result === false) {
-            throw new \RuntimeException("Unable to seek to position.");
+            throw new \RuntimeException("Unable to rewind.");
         }
     }
 
@@ -186,8 +215,12 @@ class Stream implements StreamInterface
      */
     public function isWritable()
     {
-        $mode = $this->getMetadata("mode");
-        return $mode[0] !== "r" || strpos($mode, "+") !== false;
+        if ($this->resource === null) {
+            return false;
+        }
+
+        $mode = $this->getBasicMode();
+        return in_array($mode, self::WRITABLE_MODES);
     }
 
     /**
@@ -199,6 +232,10 @@ class Stream implements StreamInterface
      */
     public function write($string)
     {
+        if ($this->resource === null) {
+            throw new \RuntimeException("Unable to write to detached stream.");
+        }
+
         $result = false;
         if ($this->isWritable()) {
             $result = fwrite($this->resource, $string);
@@ -216,8 +253,12 @@ class Stream implements StreamInterface
      */
     public function isReadable()
     {
-        $mode = $this->getMetadata("mode");
-        return strpos($mode, "r") !== false || strpos($mode, "+") !== false;
+        if ($this->resource === null) {
+            return false;
+        }
+
+        $mode = $this->getBasicMode();
+        return in_array($mode, self::READABLE_MODES);
     }
 
     /**
@@ -232,6 +273,10 @@ class Stream implements StreamInterface
      */
     public function read($length)
     {
+        if ($this->resource === null) {
+            throw new \RuntimeException("Unable to read to detached stream.");
+        }
+
         $result = false;
         if ($this->isReadable()) {
             $result = fread($this->resource, $length);
@@ -251,6 +296,10 @@ class Stream implements StreamInterface
      */
     public function getContents()
     {
+        if ($this->resource === null) {
+            throw new \RuntimeException("Unable to read to detached stream.");
+        }
+
         $result = false;
         if ($this->isReadable()) {
             $result = stream_get_contents($this->resource);
@@ -268,13 +317,17 @@ class Stream implements StreamInterface
      * stream_get_meta_data() function.
      *
      * @link http://php.net/manual/en/function.stream-get-meta-data.php
-     * @param string $key Specific metadata to retrieve.
+     * @param string|null $key Specific metadata to retrieve.
      * @return array|mixed|null Returns an associative array if no key is
      *     provided. Returns a specific key value if a key is provided and the
      *     value is found, or null if the key is not found.
      */
     public function getMetadata($key = null)
     {
+        if ($this->resource === null) {
+            return null;
+        }
+
         $metadata = stream_get_meta_data($this->resource);
         if ($key === null) {
             return $metadata;
@@ -282,4 +335,14 @@ class Stream implements StreamInterface
             return $metadata[$key];
         }
     }
+
+    /**
+     * @return string Mode for the resource reduced to only the characters
+     *   r, w, a, x, c, and + needed to determine readable and writeable status.
+     */
+    private function getBasicMode()
+    {
+        $mode = $this->getMetadata('mode') ?? '';
+        return preg_replace('/[^rwaxc+]/', '', $mode);
+    }
 }
diff --git a/test/tests/unit/Message/StreamTest.php b/test/tests/unit/Message/StreamTest.php
index 714b981..b89db9f 100644
--- a/test/tests/unit/Message/StreamTest.php
+++ b/test/tests/unit/Message/StreamTest.php
@@ -13,14 +13,14 @@ class StreamTest extends TestCase
     private $resourceDevNull;
     private $content = "Hello, world!";
 
-    public function setUp(): void
+    protected function setUp(): void
     {
         $this->resource = fopen("php://memory", "w+");
         $this->resourceDevNull = fopen("/dev/null", "r");
         fwrite($this->resource, $this->content);
     }
 
-    public function tearDown(): void
+    protected function tearDown(): void
     {
         if (is_resource($this->resource)) {
             fclose($this->resource);
@@ -269,4 +269,119 @@ class StreamTest extends TestCase
             ["c+", true,  true]
         ];
     }
+
+    // -------------------------------------------------------------------------
+    // After Detach
+
+    public function testAfterDetachToStringReturnsEmptyString(): void
+    {
+        $stream = new Stream($this->resource);
+        $stream->detach();
+        $this->assertEquals('', (string) $stream);
+    }
+
+    public function testAfterDetachCloseDoesNothing(): void
+    {
+        $stream = new Stream($this->resource);
+        $stream->detach();
+        $stream->close();
+        $this->assertTrue(true);
+    }
+
+    public function testAfterDetachDetachReturnsNull(): void
+    {
+        $stream = new Stream($this->resource);
+        $stream->detach();
+        $this->assertNull($stream->detach());
+    }
+
+    public function testAfterDetachGetSizeReturnsNull(): void
+    {
+        $stream = new Stream($this->resource);
+        $stream->detach();
+        $this->assertNull($stream->getSize());
+    }
+
+    public function testAfterDetachTellThrowsRuntimeException(): void
+    {
+        $stream = new Stream($this->resource);
+        $stream->detach();
+        $this->expectException(RuntimeException::class);
+        $stream->tell();
+    }
+
+    public function testAfterDetachEofReturnsTrue(): void
+    {
+        $stream = new Stream($this->resource);
+        $stream->detach();
+        $this->assertTrue($stream->eof());
+    }
+
+    public function testAfterDetachIsSeekableReturnsFalse(): void
+    {
+        $stream = new Stream($this->resource);
+        $stream->detach();
+        $this->assertFalse($stream->isSeekable());
+    }
+
+    public function testAfterDetachSeekThrowsRuntimeException(): void
+    {
+        $stream = new Stream($this->resource);
+        $stream->detach();
+        $this->expectException(RuntimeException::class);
+        $stream->seek(0);
+    }
+
+    public function testAfterDetachRewindThrowsRuntimeException(): void
+    {
+        $stream = new Stream($this->resource);
+        $stream->detach();
+        $this->expectException(RuntimeException::class);
+        $stream->rewind();
+    }
+
+    public function testAfterDetachIsWritableReturnsFalse(): void
+    {
+        $stream = new Stream($this->resource);
+        $stream->detach();
+        $this->assertFalse($stream->isWritable());
+    }
+
+    public function testAfterDetachWriteThrowsRuntimeException(): void
+    {
+        $stream = new Stream($this->resource);
+        $stream->detach();
+        $this->expectException(RuntimeException::class);
+        $stream->write('bork');
+    }
+
+    public function testAfterDetachIsReadableReturnsFalse(): void
+    {
+        $stream = new Stream($this->resource);
+        $stream->detach();
+        $this->assertFalse($stream->isReadable());
+    }
+
+    public function testAfterDetachReadThrowsRuntimeException(): void
+    {
+        $stream = new Stream($this->resource);
+        $stream->detach();
+        $this->expectException(RuntimeException::class);
+        $stream->read(10);
+    }
+
+    public function testAfterDetachGetContentsThrowsRuntimeException(): void
+    {
+        $stream = new Stream($this->resource);
+        $stream->detach();
+        $this->expectException(RuntimeException::class);
+        $stream->getContents();
+    }
+
+    public function testAfterDetachGetMetadataReturnsNull(): void
+    {
+        $stream = new Stream($this->resource);
+        $stream->detach();
+        $this->assertNull($stream->getMetadata());
+    }
 }