diff --git a/src/Pecee/SimpleRouter/ClassLoader/ClassLoader.php b/src/Pecee/SimpleRouter/ClassLoader/ClassLoader.php
index 77c9978..82e18ee 100644
--- a/src/Pecee/SimpleRouter/ClassLoader/ClassLoader.php
+++ b/src/Pecee/SimpleRouter/ClassLoader/ClassLoader.php
@@ -27,11 +27,11 @@ class ClassLoader implements IClassLoader
      * @param object $class
      * @param string $method
      * @param array $parameters
-     * @return mixed
+     * @return string
      */
-    public function loadClassMethod($class, string $method, array $parameters)
+    public function loadClassMethod($class, string $method, array $parameters): string
     {
-        return call_user_func_array([$class, $method], array_values($parameters));
+        return (string)call_user_func_array([$class, $method], array_values($parameters));
     }
 
     /**
@@ -39,11 +39,11 @@ class ClassLoader implements IClassLoader
      *
      * @param Callable $closure
      * @param array $parameters
-     * @return mixed
+     * @return string
      */
-    public function loadClosure(Callable $closure, array $parameters)
+    public function loadClosure(callable $closure, array $parameters): string
     {
-        return call_user_func_array($closure, array_values($parameters));
+        return (string)call_user_func_array($closure, array_values($parameters));
     }
 
 }
\ No newline at end of file
diff --git a/src/Pecee/SimpleRouter/Router.php b/src/Pecee/SimpleRouter/Router.php
index c00c8d5..ff12732 100644
--- a/src/Pecee/SimpleRouter/Router.php
+++ b/src/Pecee/SimpleRouter/Router.php
@@ -427,7 +427,7 @@ class Router
                     $routeOutput = $route->renderRoute($this->request, $this);
 
                     if ($this->renderMultipleRoutes === true) {
-                        if ($routeOutput !== null) {
+                        if ($routeOutput !== '') {
                             return $routeOutput;
                         }