diff --git a/Storage/src/StreamWrapper.php b/Storage/src/StreamWrapper.php
index 630ae47c5044..9b9304f05d83 100644
--- a/Storage/src/StreamWrapper.php
+++ b/Storage/src/StreamWrapper.php
@@ -23,7 +23,7 @@
 
 /**
  * A streamWrapper implementation for handling `gs://bucket/path/to/file.jpg`.
- * Note that you can only open a file with mode 'r', 'rb', 'rt', 'w', 'wb', 'wt', 'a', 'ab', or 'at'.
+ * Note that you can only open a file with mode 'r', 'rb', 'rt', 'w', 'wb', 'wt', 'a', 'ab', 'at', 'x', 'xb', or 'xt'.
  *
  * See: http://php.net/manual/en/class.streamwrapper.php
  */
@@ -211,7 +211,8 @@ public static function getClient($protocol = null)
      * download the file to see if it can be opened.
      *
      * @param string $path The path of the resource to open
-     * @param string $mode The fopen mode. Currently supports ('r', 'rb', 'rt', 'w', 'wb', 'wt', 'a', 'ab', 'at')
+     * @param string $mode The fopen mode. Currently supports ('r', 'rb', 'rt',
+     *        'w', 'wb', 'wt', 'a', 'ab', 'at', 'x', 'xb', 'xt')
      * @param int $flags Bitwise options STREAM_USE_PATH|STREAM_REPORT_ERRORS|STREAM_MUST_SEEK
      * @param string $openedPath Will be set to the path on success if STREAM_USE_PATH option is set
      * @return bool
@@ -264,6 +265,22 @@ public function stream_open($path, $mode, $flags, &$openedPath)
                     $options + ['name' => $name]
                 )
             );
+        } elseif ($mode == 'x') {
+            try {
+                if ($this->bucket->object($this->file)->exists()) {
+                    return $this->returnError('File already exists.', $flags);
+                }
+            } catch (ServiceException $ex) {
+                return $this->returnError($ex->getMessage(), $flags);
+            }
+
+            $this->stream = new WriteStream(null, $options);
+            $this->stream->setUploader(
+                $this->bucket->getStreamableUploader(
+                    $this->stream,
+                    $options + ['name' => $this->file, 'ifGenerationMatch' => 0]
+                )
+            );
         } elseif ($mode == 'r') {
             try {
                 // Lazy read from the source
diff --git a/Storage/tests/System/StreamWrapper/WriteTest.php b/Storage/tests/System/StreamWrapper/WriteTest.php
index a7f0d93f80ae..9c4d47602db0 100644
--- a/Storage/tests/System/StreamWrapper/WriteTest.php
+++ b/Storage/tests/System/StreamWrapper/WriteTest.php
@@ -80,4 +80,30 @@ public function testStreamingWrite()
 
         $this->assertFileExists($this->fileUrl);
     }
+
+    public function testFwriteWithXMode()
+    {
+        $this->assertFileDoesNotExist($this->fileUrl);
+
+        $output = 'This is a test with x mode';
+        $fd = fopen($this->fileUrl, 'x');
+        $this->assertIsResource($fd);
+        $this->assertEquals(strlen($output), fwrite($fd, $output));
+        $this->assertTrue(fclose($fd));
+
+        $this->assertFileExists($this->fileUrl);
+    }
+
+    public function testFwriteWithXModeFailsIfExists()
+    {
+        $this->assertFileDoesNotExist($this->fileUrl);
+
+        // Create the file first
+        touch($this->fileUrl);
+        $this->assertFileExists($this->fileUrl);
+
+        // Try to open with 'x' mode, should fail
+        $fd = @fopen($this->fileUrl, 'x');
+        $this->assertFalse($fd);
+    }
 }
diff --git a/Storage/tests/Unit/StreamWrapperTest.php b/Storage/tests/Unit/StreamWrapperTest.php
index 03c24009d809..5b462afc4898 100644
--- a/Storage/tests/Unit/StreamWrapperTest.php
+++ b/Storage/tests/Unit/StreamWrapperTest.php
@@ -83,10 +83,67 @@ public function testOpeningNonExistentFileReturnsFalse()
      */
     public function testUnknownOpenMode()
     {
+        $fp = @fopen('gs://my_bucket/existing_file.txt', 'z');
+        $this->assertFalse($fp);
+    }
+
+    /**
+     * @group storageWrite
+     */
+    public function testOpeningExistingFileWithXModeReturnsFalse()
+    {
+        $object = $this->prophesize(StorageObject::class);
+        $object->exists()->willReturn(true);
+        $this->bucket->object('existing_file.txt')->willReturn($object->reveal());
+
         $fp = @fopen('gs://my_bucket/existing_file.txt', 'x');
         $this->assertFalse($fp);
     }
 
+    /**
+     * @group storageWrite
+     */
+    public function testOpeningNonExistentFileWithXModeSucceeds()
+    {
+        $object = $this->prophesize(StorageObject::class);
+        $object->exists()->willReturn(false);
+        $this->bucket->object('new_file.txt')->willReturn($object->reveal());
+
+        $uploader = $this->prophesize(StreamableUploader::class);
+        $uploader->upload()->shouldBeCalled();
+        $uploader->getResumeUri()->willReturn('https://resume-uri/');
+        
+        $this->bucket->getStreamableUploader(Argument::any(), Argument::withEntry('ifGenerationMatch', 0))
+            ->willReturn($uploader->reveal());
+
+        $fp = fopen('gs://my_bucket/new_file.txt', 'x');
+        $this->assertIsResource($fp);
+        fwrite($fp, "some data");
+        fclose($fp);
+    }
+
+    /**
+     * @group storageWrite
+     */
+    public function testOpeningNonExistentFileWithXbModeSucceeds()
+    {
+        $object = $this->prophesize(StorageObject::class);
+        $object->exists()->willReturn(false);
+        $this->bucket->object('new_file.txt')->willReturn($object->reveal());
+
+        $uploader = $this->prophesize(StreamableUploader::class);
+        $uploader->upload()->shouldBeCalled();
+        $uploader->getResumeUri()->willReturn('https://resume-uri/');
+
+        $this->bucket->getStreamableUploader(Argument::any(), Argument::withEntry('ifGenerationMatch', 0))
+            ->willReturn($uploader->reveal());
+
+        $fp = fopen('gs://my_bucket/new_file.txt', 'xb');
+        $this->assertIsResource($fp);
+        fwrite($fp, "some data");
+        fclose($fp);
+    }
+
     /**
      * @group storageRead
      */