diff --git a/cmd/prometheus/main.go b/cmd/prometheus/main.go
index 787a28992..1d844ddba 100644
--- a/cmd/prometheus/main.go
+++ b/cmd/prometheus/main.go
@@ -343,7 +343,7 @@ func main() {
 	a.Flag("web.page-title", "Document title of Prometheus instance.").
 		Default("Prometheus Time Series Collection and Processing Server").StringVar(&cfg.web.PageTitle)
 
-	a.Flag("web.cors.origin", `Regex for CORS origin. It is fully anchored. Example: 'https?://(domain1\|domain2)\.com'`).
+	a.Flag("web.cors.origin", `Regex for CORS origin. It is fully anchored. Example: 'https?://(domain1|domain2)\.com'`).
 		Default(".*").StringVar(&cfg.corsRegexString)
 
 	serverOnlyFlag(a, "storage.tsdb.path", "Base path for metrics storage.").