diff --git a/src/JsonSchema/Constraints/TypeConstraint.php b/src/JsonSchema/Constraints/TypeConstraint.php
index 0ef32843..efc0abbc 100644
--- a/src/JsonSchema/Constraints/TypeConstraint.php
+++ b/src/JsonSchema/Constraints/TypeConstraint.php
@@ -134,7 +134,7 @@ protected function implodeWith(array $elements, $delimiter = ', ', $listEnd = fa
      */
     protected function validateTypeNameWording($type)
     {
-        if (!isset(self::$wording[$type])) {
+        if (!array_key_exists($type, self::$wording)) {
             throw new StandardUnexpectedValueException(
                 sprintf(
                     'No wording for %s available, expected wordings are: [%s]',