diff --git a/appveyor.yml b/appveyor.yml
index b67258e2..f864c5a9 100644
--- a/appveyor.yml
+++ b/appveyor.yml
@@ -19,7 +19,7 @@ environment:
 install:
   - python -m pip install --upgrade pip wheel setuptools
 before_build:
-  - ps: psql -d "postgresql://$ENV:VNPY_TEST_POSTGRESQL_USER:$ENV:VNPY_TEST_POSTGRESQL_PASSWORD@localhost" -c "create database vnpy;"
+  - ps: psql -d "postgresql://${ENV:VNPY_TEST_POSTGRESQL_USER}:${ENV:VNPY_TEST_POSTGRESQL_PASSWORD}@localhost" -c "create database vnpy;"
   - ps: . "C:\Program Files\MySQL\MySQL Server 5.7\bin\mysql" -u $ENV:VNPY_TEST_MYSQL_USER -e 'CREATE DATABASE vnpy;'
 
 build_script: