diff --git a/guix-data-service/web/html-utils.scm b/guix-data-service/web/html-utils.scm
index d38c448..ab2fa85 100644
--- a/guix-data-service/web/html-utils.scm
+++ b/guix-data-service/web/html-utils.scm
@@ -67,7 +67,8 @@
      ("failed-dependency" . "Failed (dependency)")
      ("failed-other" . "Failed (other)")
      ("canceled" . "Canceled")
-     ("" . "Unknown"))
+     ("" . "Unknown")
+     (#f . "Unknown"))
    value))
 
 (define (build-url build-server-id build-server-build-id derivation-file-name)
@@ -110,7 +111,8 @@
                         ("failed-dependency" . "warning")
                         ("failed-other" . "danger")
                         ("canceled" . "default")
-                        ("" . "default"))
+                        ("" . "default")
+                        (#f . "default"))
                       status)))
             (style "display: inline-block; font-size: 1.2em; margin-top: 0.4em; margin-bottom: 0.4em;"))
          ,(build-status-value->display-string status)))