diff --git a/src/html-utils.lisp b/src/html-utils.lisp
index 4e1bf1a..f5bf7b3 100644
--- a/src/html-utils.lisp
+++ b/src/html-utils.lisp
@@ -135,7 +135,7 @@
 
 (defun footnote-reference-re (&key (enforce-end-string t))
   (format nil
-          "(~a[~a]+)?~@[$~]"
+          "(~a[~a]+)~@[$~]"
           #\ZERO_WIDTH_SPACE
           +digits-superscripts+
           enforce-end-string))