diff --git a/defaults/main.yml b/defaults/main.yml
index 50c3b88..20a0dad 100644
--- a/defaults/main.yml
+++ b/defaults/main.yml
@@ -39,6 +39,7 @@ wordpress_php_prereq:
   - 'php{{ php_version }}-curl'
   - 'php{{ php_version }}-opcache'
   - 'php{{ php_version }}-xml'
+  - 'php{{ php_version }}-mbstring'
   - php-pear
   - php-date
   - imagemagick