diff --git a/js/index.mjs b/js/index.mjs
index f4864af..a310d10 100644
--- a/js/index.mjs
+++ b/js/index.mjs
@@ -52,6 +52,7 @@ export class PMTiles {
                     }
                 })
             } else {
+                console.log("Check failed: if you know this server supports byte serving, pass allow_200: true")
                 throw new Error("Invalid response: " + resp.status)
             }
         })