diff --git a/.env.sample b/.env.sample
index 6d2affa..f447a75 100644
--- a/.env.sample
+++ b/.env.sample
@@ -1,5 +1,6 @@
 FLASK_DEBUG=True
-# Expects a full tenant name such as "contoso.onmicrosoft.com", or its GUID
-TENANT_ID=<tenant id>
+# Expects a full tenant id such as "contoso.onmicrosoft.com", or its GUID
+# Or leave it undefined if you are building a multi-tenant app
+#TENANT_ID=<tenant id>
 CLIENT_ID=<client id>
 CLIENT_SECRET=<client secret>
diff --git a/app_config.py b/app_config.py
index 2ba53ff..2c96709 100644
--- a/app_config.py
+++ b/app_config.py
@@ -6,7 +6,7 @@
 CLIENT_SECRET = os.getenv("CLIENT_SECRET")
 
 # AUTHORITY = "https://login.microsoftonline.com/common"  # For multi-tenant app
-AUTHORITY = f"https://login.microsoftonline.com/{os.getenv('TENANT_ID')}"
+AUTHORITY = f"https://login.microsoftonline.com/{os.getenv('TENANT_ID', 'common')}"
 
 REDIRECT_PATH = "/getAToken"  # Used for forming an absolute URL to your redirect URI.
 # The absolute URL must match the redirect URI you set