diff --git a/upgrade_roundcube.sh b/upgrade_roundcube.sh
index 161e09d..9896d3d 100755
--- a/upgrade_roundcube.sh
+++ b/upgrade_roundcube.sh
@@ -154,6 +154,13 @@ fi
 DEFAULT_DB_HOST="localhost"
 DEFAULT_DB_NAME="roundcubemail"
 DEFAULT_DB_USER="roundcube"
+if [[ -f "/usr/local/mysql/sys-maint.cnf" ]] ; then
+   DEFAULT_MYSQL_CREDENTIALS="--defaults-file=/usr/local/mysql/sys-maint.cnf"
+elif [[ -f "/etc/mysql/debian.cnf" ]] ; then
+   DEFAULT_MYSQL_CREDENTIALS="--defaults-file=/etc/mysql/debian.cnf"
+else
+   DEFAULT_MYSQL_CREDENTIALS=""
+fi
 DEFAULT_DEBIAN_MYSQL_CREDENTIALS="--defaults-file=/etc/mysql/debian.cnf"
 DEFAULT_MYSQL_CREDENTIALS="--defaults-file=/usr/local/mysql/sys-maint.cnf"