diff --git a/src/JWT.php b/src/JWT.php
index 6d30e941..d45052cf 100644
--- a/src/JWT.php
+++ b/src/JWT.php
@@ -98,6 +98,9 @@ public static function decode($jwt, $key, $allowed_algs = array())
         }
         if (is_array($key) || $key instanceof \ArrayAccess) {
             if (isset($header->kid)) {
+                if (!isset($key[$header->kid])) {
+                    throw new UnexpectedValueException('"kid" invalid, unable to lookup correct key');
+                }
                 $key = $key[$header->kid];
             } else {
                 throw new UnexpectedValueException('"kid" empty, unable to lookup correct key');