diff --git a/src/Illuminate/Routing/UrlGenerator.php b/src/Illuminate/Routing/UrlGenerator.php
index 7a87d5118297..e1dd34af1363 100755
--- a/src/Illuminate/Routing/UrlGenerator.php
+++ b/src/Illuminate/Routing/UrlGenerator.php
@@ -320,19 +320,9 @@ public function formatScheme($secure = null)
      */
     public function signedRoute($name, $parameters = [], $expiration = null, $absolute = true)
     {
-        $parameters = $this->formatParameters($parameters);
-
-        if (array_key_exists('signature', $parameters)) {
-            throw new InvalidArgumentException(
-                '"Signature" is a reserved parameter when generating signed routes. Please rename your route parameter.'
-            );
-        }
-
-        if (array_key_exists('expires', $parameters)) {
-            throw new InvalidArgumentException(
-                '"Expires" is a reserved parameter when generating signed routes. Please rename your route parameter.'
-            );
-        }
+        $this->ensureSignedRouteParametersAreNotReserved(
+            $parameters = $this->formatParameters($parameters)
+        );
 
         if ($expiration) {
             $parameters = $parameters + ['expires' => $this->availableAt($expiration)];
@@ -347,6 +337,27 @@ public function signedRoute($name, $parameters = [], $expiration = null, $absolu
         ], $absolute);
     }
 
+    /**
+     * Ensure the given signed route parameters are not reserved.
+     *
+     * @param  mixed  $parameters
+     * @return void
+     */
+    protected function ensureSignedRouteParametersAreNotReserved($parameters)
+    {
+        if (array_key_exists('signature', $parameters)) {
+            throw new InvalidArgumentException(
+                '"Signature" is a reserved parameter when generating signed routes. Please rename your route parameter.'
+            );
+        }
+
+        if (array_key_exists('expires', $parameters)) {
+            throw new InvalidArgumentException(
+                '"Expires" is a reserved parameter when generating signed routes. Please rename your route parameter.'
+            );
+        }
+    }
+
     /**
      * Create a temporary signed route URL for a named route.
      *