diff --git a/PHPUnit/Framework/Assert.php b/PHPUnit/Framework/Assert.php
index db8e7375afc..da489f8cd4b 100644
--- a/PHPUnit/Framework/Assert.php
+++ b/PHPUnit/Framework/Assert.php
@@ -78,7 +78,7 @@ public static function assertArrayHasKey($key, $array, $message = '')
         }
         if (!(is_array($array) || $array instanceof ArrayAccess)) {
             throw PHPUnit_Util_InvalidArgumentHelper::factory(
-              1, 'array or ArrayAccess'
+              2, 'array or ArrayAccess'
             );
         }
 
@@ -104,7 +104,7 @@ public static function assertArrayNotHasKey($key, $array, $message = '')
         }
         if (!(is_array($array) || $array instanceof ArrayAccess)) {
             throw PHPUnit_Util_InvalidArgumentHelper::factory(
-              1, 'array or ArrayAccess'
+              2, 'array or ArrayAccess'
             );
         }
 
@@ -2376,6 +2376,7 @@ public static function isTrue()
     /**
      * Returns a PHPUnit_Framework_Constraint_Callback matcher object.
      *
+     * @param callable $callback
      * @return PHPUnit_Framework_Constraint_Callback
      */
     public static function callback($callback)
diff --git a/PHPUnit/Framework/Assert/Functions.php b/PHPUnit/Framework/Assert/Functions.php
index 057a950175e..2b0e04ca412 100644
--- a/PHPUnit/Framework/Assert/Functions.php
+++ b/PHPUnit/Framework/Assert/Functions.php
@@ -1699,11 +1699,12 @@ function isTrue()
 /**
  * Returns a PHPUnit_Framework_Constraint_Callback matcher object.
  *
+ * @param callable $callback
  * @return PHPUnit_Framework_Constraint_Callback
  */
-function callback()
+function callback($callback)
 {
-    return PHPUnit_Framework_Assert::callback();
+    return PHPUnit_Framework_Assert::callback($callback);
 }
 
 /**
diff --git a/PHPUnit/Framework/Constraint/Callback.php b/PHPUnit/Framework/Constraint/Callback.php
index 7a3340dcf7a..dbc33ceb90b 100644
--- a/PHPUnit/Framework/Constraint/Callback.php
+++ b/PHPUnit/Framework/Constraint/Callback.php
@@ -58,7 +58,7 @@ class PHPUnit_Framework_Constraint_Callback extends PHPUnit_Framework_Constraint
     private $callback;
 
     /**
-     * @param callable $value
+     * @param callable $callback
      * @throws InvalidArgumentException
      */
     public function __construct($callback)
diff --git a/PHPUnit/Framework/Constraint/JsonMatches.php b/PHPUnit/Framework/Constraint/JsonMatches.php
index 01bb70b8e8d..de3ed61c174 100644
--- a/PHPUnit/Framework/Constraint/JsonMatches.php
+++ b/PHPUnit/Framework/Constraint/JsonMatches.php
@@ -83,13 +83,13 @@ public function __construct($value)
     protected function matches($other)
     {
         $decodedOther = json_decode($other);
-        if (!is_object($decodedOther)) {
+        if (json_last_error()) {
             $this->failure_reason = $this->getJsonError();
             return FALSE;
         }
 
         $decodedValue = json_decode($this->value);
-        if (!is_object($decodedValue)) {
+        if (json_last_error()) {
             $this->failure_reason = $this->getJsonError();
             return FALSE;
         }
@@ -123,4 +123,4 @@ public function toString()
             $this->value
         );
     }
-}
\ No newline at end of file
+}