diff --git a/guix-data-service/web/controller.scm b/guix-data-service/web/controller.scm
index bfdbd18..0841ae1 100644
--- a/guix-data-service/web/controller.scm
+++ b/guix-data-service/web/controller.scm
@@ -498,7 +498,8 @@
         (render-html
          #:sxml (general-not-found
                  "Derivation not found"
-                 "No derivation found with this file name.")
+                 "Derivations can differ, but produce the same outputs, so try querying by
+output, rather than derivation file name.")
          #:code 404))))
 
 (define (render-json-derivation derivation-file-name)