diff --git a/postgres-dump-zstd-docker-sock.sh b/postgres-dump-zstd-docker-sock.sh
index c9d4f90..a5bd4cc 100755
--- a/postgres-dump-zstd-docker-sock.sh
+++ b/postgres-dump-zstd-docker-sock.sh
@@ -10,22 +10,22 @@ log() {
 
 print_usage() {
   cat <<EOF >&2
-Usage: $0 --socket=PATH --api-version=VERSION --container=NAME --backup-dir=DIR --backup-prefix=PREFIX
+Usage: $0 [--socket=PATH] [--api-version=VERSION] --container=NAME [--backup-dir=DIR] --backup-prefix=PREFIX
 
 Options:
-  --socket=PATH           Docker Engine unix socket path
-  --api-version=VERSION   Docker API version (e.g. v1.51)
+  --socket=PATH           Docker Engine unix socket path (default: /var/run/docker.sock)
+  --api-version=VERSION   Docker API version (default: v1.51)
   --container=NAME        PostgreSQL container name
-  --backup-dir=DIR        Directory to store backups
+  --backup-dir=DIR        Directory to store backups (default: /backups)
   --backup-prefix=PREFIX  Backup filename prefix
   --help                  Show this help message
 EOF
 }
 
-DOCKER_SOCKET=""
-DOCKER_API_VERSION=""
+DOCKER_SOCKET="/var/run/docker.sock"
+DOCKER_API_VERSION="v1.51"
 PG_CONTAINER_NAME=""
-BACKUP_DIR=""
+BACKUP_DIR="/backups"
 BACKUP_PREFIX=""
 
 missing_value() {