diff --git a/doc/d-utils.md b/doc/d-utils.md
index 0724989..64ce1df 100644
--- a/doc/d-utils.md
+++ b/doc/d-utils.md
@@ -552,4 +552,4 @@ Converts list of pairs into BST dictionary.
                 proc
                 (v #f))
 
-
+Functional update with optional default value (defaults to #f).
diff --git a/src/util-bst.scm b/src/util-bst.scm
index 9afa8d8..dd73d53 100644
--- a/src/util-bst.scm
+++ b/src/util-bst.scm
@@ -16,7 +16,6 @@
 
   bst-set
   bst-remove
-  ;; bst-update
 
   bst-keys
 
@@ -352,7 +351,7 @@
 		      (cons EQ? <?))))))
 
  (define*/doc (bst-update bst k proc (v #f))
-   ("")
+   ("Functional update with optional default value (defaults to #f).")
    (let-comparators
     (EQ? <? bst)
     (let-values	(((new-root add-count)