diff --git a/.env b/.env
index b5429de025..090057c08d 100644
--- a/.env
+++ b/.env
@@ -1,10 +1,18 @@
+# to define environment variables available to docker-compose.yml
+
 IMAGE_REPO=milvusdb
 IMAGE_ARCH=amd64
 OS_NAME=ubuntu20.04
+
+# for services.builder.image in docker-compose.yml
 DATE_VERSION=20231212-4651f89
 LATEST_DATE_VERSION=20231212-4651f89
+
+# for services.gpubuilder.image in docker-compose.yml
 GPU_DATE_VERSION=20231212-4651f89
 LATEST_GPU_DATE_VERSION=20231212-4651f89
+
+# for other services in docker-compose.yml
 MINIO_ADDRESS=minio:9000
 PULSAR_ADDRESS=pulsar://pulsar:6650
 ETCD_ENDPOINTS=etcd:2379
diff --git a/build/builder.sh b/build/builder.sh
index 5e58b7f07f..b01f243082 100755
--- a/build/builder.sh
+++ b/build/builder.sh
@@ -6,7 +6,9 @@ set -euo pipefail
 toplevel=$(dirname "$(cd "$(dirname "${0}")"; pwd)")
 
 if [[ -f "$toplevel/.env" ]]; then
-  export $(cat $toplevel/.env | xargs)
+    set -a  # automatically export all variables from .env
+    source $toplevel/.env
+    set +a  # stop automatically exporting
 fi
 
 pushd "${toplevel}"