diff --git a/doc/build.scm b/doc/build.scm
index c2d2d3939f..47cff15985 100644
--- a/doc/build.scm
+++ b/doc/build.scm
@@ -671,8 +671,8 @@ (define* (base-language-url code manual
                                         #:key split-node?)
               ;; Return the base URL of MANUAL for language CODE.
               (if split-node?
-                  (string-append "../../" code "/html_node")
-                  (string-append "../" code "/" manual
+                  (string-append "../../" (normalize code) "/html_node")
+                  (string-append "../" (normalize code) "/" manual
                                  (if (string=? code "en")
                                      ""
                                      (string-append "." code))