diff --git a/server-mysql/ubuntu/Dockerfile b/server-mysql/ubuntu/Dockerfile
index fe7ca3064..2a0734e71 100644
--- a/server-mysql/ubuntu/Dockerfile
+++ b/server-mysql/ubuntu/Dockerfile
@@ -15,7 +15,7 @@ RUN set -eux && \
     groupadd --system --gid 1995 zabbix && \
     useradd \
             --system --comment "Zabbix monitoring system" \
-            -g zabbix -G root -G dialout \
+            -g zabbix -G root,dialout \
             --uid 1997 \
             --shell /sbin/nologin \
             --home-dir /var/lib/zabbix/ \
diff --git a/server-pgsql/ubuntu/Dockerfile b/server-pgsql/ubuntu/Dockerfile
index 540481e4c..b0b8c25a9 100644
--- a/server-pgsql/ubuntu/Dockerfile
+++ b/server-pgsql/ubuntu/Dockerfile
@@ -15,7 +15,7 @@ RUN set -eux && \
     groupadd --system --gid 1995 zabbix && \
     useradd \
             --system --comment "Zabbix monitoring system" \
-            -g zabbix -G root -G dialout \
+            -g zabbix -G root,dialout \
             --uid 1997 \
             --shell /sbin/nologin \
             --home-dir /var/lib/zabbix/ \