symfony
diff --git a/‎src/Symfony/Component/Routing/RouteCollection.php
Copy file name to clipboardExpand all lines: src/Symfony/Component/Routing/RouteCollection.php
+4Lines changed: 4 additions & 0 deletions b/‎src/Symfony/Component/Routing/RouteCollection.php
Copy file name to clipboardExpand all lines: src/Symfony/Component/Routing/RouteCollection.php
+4Lines changed: 4 additions & 0 deletions
diff --git a/‎src/Symfony/Component/Routing/RouteCollectionBuilder.php
Copy file name to clipboardExpand all lines: src/Symfony/Component/Routing/RouteCollectionBuilder.php
+3-1Lines changed: 3 additions & 1 deletion b/‎src/Symfony/Component/Routing/RouteCollectionBuilder.php
Copy file name to clipboardExpand all lines: src/Symfony/Component/Routing/RouteCollectionBuilder.php
+3-1Lines changed: 3 additions & 1 deletion
@@ -140,6 +140,10 @@ public function addCollection(self $collection)
      */
     public function addPrefix($prefix, array $defaults = [], array $requirements = [])
     {
+        if (null === $prefix) {
+            @trigger_error(sprintf('Passing null as $prefix to %s is deprecated in Symfony 4.4 and will trigger a TypeError in 5.0.', __METHOD__), E_USER_DEPRECATED);
+        }
+
         $prefix = trim(trim($prefix), '/');
 
         if ('' === $prefix) {
 
@@ -309,7 +309,9 @@ public function build()
             } else {
                 /* @var self $route */
                 $subCollection = $route->build();
-                $subCollection->addPrefix($this->prefix);
+                if (null !== $this->prefix) {
+                    $subCollection->addPrefix($this->prefix);
+                }
 
                 $routeCollection->addCollection($subCollection);
             }