diff --git a/src/ConfigPostProcessor.php b/src/ConfigPostProcessor.php
index f704e3c..c3b601a 100644
--- a/src/ConfigPostProcessor.php
+++ b/src/ConfigPostProcessor.php
@@ -5,8 +5,6 @@
 use function array_intersect_key;
 use function array_key_exists;
 use function array_pop;
-use function array_push;
-use function count;
 use function in_array;
 use function is_array;
 use function is_callable;
@@ -70,7 +68,7 @@ function ($value) {
             function ($value, array $keys) {
                 $key = array_pop($keys);
                 // Only worried about a top-level "router" key.
-                return $key === 'router' && count($keys) === 0 && is_array($value)
+                return $key === 'router' && $keys === [] && is_array($value)
                     ? [$this, 'noopReplacement']
                     : null;
             },
@@ -84,7 +82,7 @@ function ($value) {
 
             // Array values
             function ($value, array $keys) {
-                return 0 !== count($keys) && is_array($value)
+                return $keys !== [] && is_array($value)
                     ? [$this, '__invoke']
                     : null;
             },
@@ -153,7 +151,7 @@ private function replace($value, array $keys, $key = null)
     {
         // Add new key to the list of keys.
         // We do not need to remove it later, as we are working on a copy of the array.
-        array_push($keys, $key);
+        $keys[] = $key;
 
         // Identify rewrite strategy and perform replacements
         $rewriteRule = $this->replacementRuleMatch($value, $keys);