diff --git a/src/util-bst-ldict.scm b/src/util-bst-ldict.scm
index 8dba565..1810793 100644
--- a/src/util-bst-ldict.scm
+++ b/src/util-bst-ldict.scm
@@ -29,8 +29,10 @@
  (define (ldict<? a b)
    (if (number? a)
        (< a b)
-       (string<? (symbol->string a)
-		 (symbol->string b))))
+       (if (string? a)
+	   (string<? a b)
+	   (string<? (symbol->string a)
+		     (symbol->string b)))))
 
  (define (make-ldict . equality?/pairs)
    (let ((equality? (if (or (null? equality?/pairs)