--- a/testing/geckodriver/CHANGES.md
+++ b/testing/geckodriver/CHANGES.md
@@ -10,16 +10,17 @@ All notable changes to this program is d
 
 [`FullscreenWindow`]: https://docs.rs/webdriver/0.29.0/webdriver/command/enum.WebDriverCommand.html#variant.FullscreenWindow
 [`GetWindowRect`]: https://docs.rs/webdriver/0.29.0/webdriver/command/enum.WebDriverCommand.html#variant.GetWindowRect
 [`MaximizeWindow`]: https://docs.rs/webdriver/0.29.0/webdriver/command/enum.WebDriverCommand.html#variant.MaximizeWindow
 [`MinimizeWindow`]: https://docs.rs/webdriver/0.29.0/webdriver/command/enum.WebDriverCommand.html#variant.MinimizeWindow
 [`SetWindowRect`]: https://docs.rs/webdriver/0.29.0/webdriver/command/enum.WebDriverCommand.html#variant.SetWindowRect
 
 ### Changed
+- To make sure no browser process is left behind when the [`New Session` command](https://docs.rs/webdriver/0.27.0/webdriver/command/enum.WebDriverCommand.html#variant.NewSession) fails, the process is closed immediately now.
 - The `proxyType` `noproxy` has been replaced with `direct` in accordance with recent WebDriver specification changes
 - `/moz/addon/install` command accepts an `addon` parameter, in lieu of `path`, containing an addon as a Base64 string
 
 ## 0.18.0 (2017-07-10)
 
 ### Changed
 - [`RectResponse`](https://docs.rs/webdriver/0.27.0/webdriver/response/struct.RectResponse.html) permits returning floats for `width` and `height` fields
 - New type [`CookieResponse`](https://docs.rs/webdriver/0.27.0/webdriver/response/struct.CookieResponse.html) for the [`GetNamedCookie` command](https://docs.rs/webdriver/0.27.0/webdriver/command/enum.WebDriverCommand.html#variant.GetNamedCookie) returns a single cookie, as opposed to an array of a single cookie

--- a/testing/geckodriver/src/marionette.rs
+++ b/testing/geckodriver/src/marionette.rs
@@ -543,17 +543,26 @@ impl WebDriverHandler<GeckoExtensionRout
                 resolved_capabilities = Some(try!(
                     self.create_connection(&msg.session_id, &capabilities)));
             }
         }
 
         match self.connection.lock() {
             Ok(ref mut connection) => {
                 match connection.as_mut() {
-                    Some(conn) => conn.send_command(resolved_capabilities, &msg),
+                    Some(conn) => {
+                        conn.send_command(resolved_capabilities, &msg)
+                            .map_err(|mut err| {
+                                // Shutdown the browser if no session can
+                                // be established due to errors.
+                                if let NewSession(_) = msg.command {
+                                    err.delete_session=true;
+                                }
+                                err})
+                    },
                     None => panic!("Connection missing")
                 }
             },
             Err(_) => {
                 Err(WebDriverError::new(
                     ErrorStatus::UnknownError,
                     "Failed to aquire Marionette connection"))
             }