diff --git a/src/Container/AbstractBusFactory.php b/src/Container/AbstractBusFactory.php
index 7b3f7be..ae6f4b4 100644
--- a/src/Container/AbstractBusFactory.php
+++ b/src/Container/AbstractBusFactory.php
@@ -133,7 +133,7 @@ private function attachPlugins(MessageBus $bus, array &$utils, ContainerInterfac
         foreach ($utils as $index => $util) {
             if (! is_string($util) || ! $container->has($util)) {
                 throw new RuntimeException(sprintf(
-                    'Wrong message bus utility configured at %. Either it is not a string or unknown by the container.',
+                    'Wrong message bus utility configured at %s. Either it is not a string or unknown by the container.',
                     'prooph.service_bus.' . $this->getBusConfigKey() . '.' . $index
                 ));
             }