diff --git a/src/tad/FunctionMocker/FunctionMocker.php b/src/tad/FunctionMocker/FunctionMocker.php
index 1cd3ac1..387b21f 100644
--- a/src/tad/FunctionMocker/FunctionMocker.php
+++ b/src/tad/FunctionMocker/FunctionMocker.php
@@ -98,8 +98,8 @@ public static function tearDown() {
      * not specifying a return value will make the replaced function or value
      * return `null`.
      *
-     * @param      $functionName
-     * @param null $returnValue
+     * @param string|array $functionName
+     * @param mixed        $returnValue
      *
      * @return mixed|Call\Verifier\InstanceMethodCallVerifier|static
      */