diff --git a/install/lib/installer_base.lib.php b/install/lib/installer_base.lib.php
index 31fc67938367fc833d5807e405aa902b7546cd4e..96ef499c67f0fdb46def962c34cd24a720bc0c99 100644
--- a/install/lib/installer_base.lib.php
+++ b/install/lib/installer_base.lib.php
@@ -1496,7 +1496,7 @@ class installer_base {
 		foreach ($options as $value) {
 			$value = trim($value);
 			if ($value == '') continue;
-			if (preg_match("|check_recipient_access\s+proxy:mysql:${config_dir}/mysql-verify_recipients.cf|", $value)) {
+			if (preg_match("|check_recipient_access\s+proxy:mysql:${quoted_config_dir}/mysql-verify_recipients.cf|", $value)) {
 				continue;
 			}
 			$new_options[] = $value;