diff --git a/composer.json b/composer.json
index 6d21ae1..b3d1758 100644
--- a/composer.json
+++ b/composer.json
@@ -16,9 +16,10 @@
         }   
     ],
     "require": {
-        "php": ">=5.3.2"        
+        "php": ">=5.3.2",
+        "ext-mbstring": "*"
     },
     "autoload": {
         "psr-0": { "Sunra\\PhpSimple\\HtmlDomParser": "Src/" }
     }    
-}
\ No newline at end of file
+}