diff --git a/zerver/openapi/zulip.yaml b/zerver/openapi/zulip.yaml
index 5bccb714cf..4c60599c77 100644
--- a/zerver/openapi/zulip.yaml
+++ b/zerver/openapi/zulip.yaml
@@ -21489,7 +21489,8 @@ paths:
                               nullable: true
                               description: |
                                 URL for an image to be displayed as an icon in all buttons for
-                                the external authentication method.
+                                the external authentication method. This URL should be resolved
+                                relative to the server's base URL.
 
                                 When `null`, no icon should be displayed.
                             login_url: