diff --git a/lang/en.php b/lang/en.php
index 36c3358..8e14f78 100644
--- a/lang/en.php
+++ b/lang/en.php
@@ -23,7 +23,8 @@ return array(
     'dateFormat' => "must be date with format '%s'",
     'dateBefore' => "must be date before '%s'",
     'dateAfter' => "must be date after '%s'",
-    'contains' => "must contain %s"
+    'contains' => "must contain %s",
+    'boolean' => "must be a boolean",
 );
 
 
diff --git a/src/Valitron/Validator.php b/src/Valitron/Validator.php
index 1ee80ca..939df50 100644
--- a/src/Valitron/Validator.php
+++ b/src/Valitron/Validator.php
@@ -430,6 +430,23 @@ class Validator
         return $vtime > $ptime;
     }
 
+    /**
+     * Validate that a field contains a boolean.
+     * If $params[0] is true, it also check for string == true.
+     *
+     * @param  string  $field
+     * @param  mixed   $value
+     * @param  array   $params
+     * @return bool
+     */
+    protected function validateBoolean($field, $value, $params)
+    {
+        if(isset($params[0]) && $params[0] == true && $value == "true") {
+            $value = true;
+        }
+        return (is_bool($value)) ? true : false;
+    }
+
     /**
      *  Get array of fields and data
      */