diff --git a/.gitignore b/.gitignore
index 74efce3..4b08d9f 100755
--- a/.gitignore
+++ b/.gitignore
@@ -4,3 +4,5 @@
 # Composer.
 vendor
 composer.lock
+
+tests/assets/test.json
diff --git a/src/Mailto.php b/src/Mailto.php
index 05ea152..2164766 100644
--- a/src/Mailto.php
+++ b/src/Mailto.php
@@ -1,5 +1,5 @@
 <?php namespace Locker\XApi;
 
 class Mailto extends RegexpAtom {
-  protected static $pattern = '/^mailto:[A-Z0-9._%+-]+@[A-Z0-9.-]+\.[A-Z]{2,4}$/i';
+  protected static $pattern = '/^mailto:[A-Z0-9.\'_%+-]+@[A-Z0-9.-]+\.[A-Z]{2,4}$/i';
 }