diff --git a/core/lib/Drupal/Core/Path/CurrentPathStack.php b/core/lib/Drupal/Core/Path/CurrentPathStack.php
index 51b97cd71e..4a04173c67 100644
--- a/core/lib/Drupal/Core/Path/CurrentPathStack.php
+++ b/core/lib/Drupal/Core/Path/CurrentPathStack.php
@@ -46,7 +46,7 @@ public function __construct(RequestStack $request_stack) {
    *   (optional) The request.
    *
    * @return string
-   *   Returns the path, without leading slashes.
+   *   Returns the encoded path with a leading slash.
    */
   public function getPath(Request $request = NULL) {
     if (!isset($request)) {
@@ -63,13 +63,20 @@ public function getPath(Request $request = NULL) {
    * Sets the current path.
    *
    * @param string $path
-   *   The path.
+   *   The path, with a leading slash.
    * @param \Symfony\Component\HttpFoundation\Request $request
    *   (optional) The request.
    *
+   * @throws \LogicException
+   *   Thrown when $path does not contain a leading slash.
+   *
    * @return $this
    */
   public function setPath($path, Request $request = NULL) {
+    if (strpos($path, '/') !== 0) {
+      throw new \LogicException(sprintf('The path %s must begin with a leading slash.', $path));
+    }
+
     if (!isset($request)) {
       $request = $this->requestStack->getCurrentRequest();
     }