diff --git a/options.go b/options.go
index 3306567..c54038c 100644
--- a/options.go
+++ b/options.go
@@ -33,7 +33,7 @@ type Options struct {
 	AuthenticatedEmailsFile  string   `flag:"authenticated-emails-file" cfg:"authenticated_emails_file"`
 	AzureTenant              string   `flag:"azure-tenant" cfg:"azure_tenant"`
 	EmailDomains             []string `flag:"email-domain" cfg:"email_domains"`
-	WhitelistDomains         []string `flag:"whitelist-domains" cfg:"whitelist_domains"`
+	WhitelistDomains         []string `flag:"whitelist-domain" cfg:"whitelist_domains" env:"OAUTH2_PROXY_WHITELIST_DOMAINS"`
 	GitHubOrg                string   `flag:"github-org" cfg:"github_org"`
 	GitHubTeam               string   `flag:"github-team" cfg:"github_team"`
 	GoogleGroups             []string `flag:"google-group" cfg:"google_group"`