diff --git a/helpers/PrerequisiteChecker.php b/helpers/PrerequisiteChecker.php
index 752f6238..c42f17c2 100644
--- a/helpers/PrerequisiteChecker.php
+++ b/helpers/PrerequisiteChecker.php
@@ -4,7 +4,7 @@ class ERequirementNotMet extends Exception
 {
 }
 
-const REQUIRED_PHP_EXTENSIONS = ['fileinfo', 'pdo_sqlite', 'gd', 'ctype', 'json', 'intl', 'zlib',
+const REQUIRED_PHP_EXTENSIONS = ['fileinfo', 'pdo_sqlite', 'gd', 'ctype', 'json', 'intl', 'zlib', 'mbstring',
 	// These are core extensions, so normally can't be missing, but seems to be the case, however, on FreeBSD
 	'filter', 'iconv', 'tokenizer'
 ];