diff --git a/composer.json b/composer.json
index 74b1f97..c880927 100644
--- a/composer.json
+++ b/composer.json
@@ -26,6 +26,7 @@
 		"ext-json": "*",
 		"ext-intl": "*",
 		"ext-zlib": "*",
+		"ext-mbstring": "*",
 		"mike42/gfx-php" : "^0.6"
 	},
 	"suggest" : {