diff --git a/src/schemas/json/prometheus.json b/src/schemas/json/prometheus.json
index 6198c7e11b6..17ac5f5aa44 100644
--- a/src/schemas/json/prometheus.json
+++ b/src/schemas/json/prometheus.json
@@ -40,6 +40,9 @@
         "password": {
           "type": ["string", "null"]
         },
+        "username_file": {
+          "$ref": "#/definitions/filepath"
+        },
         "password_file": {
           "$ref": "#/definitions/filepath"
         }