diff --git a/api/management/api.go b/api/management/api.go
index 0f343463..fe7ec063 100644
--- a/api/management/api.go
+++ b/api/management/api.go
@@ -312,7 +312,7 @@ const (
 	RegExpID = `^[a-z0-9]{8}-[a-z0-9]{4}-[a-z0-9]{4}-[a-z0-9]{4}-[a-z0-9]{12}$`
 
 	// Client
-	RegExpClientID = `^[a-zA-Z0-9_-.]{1,255}$`
+	RegExpClientID = `^[a-zA-Z0-9-_.]{1,255}$`
 
 	// User
 	RegExpUsername    = `^[a-zA-Z0-9-_.]{1,128}$`