diff --git a/static/main.js b/static/main.js
index ee19a8a..eed544b 100644
--- a/static/main.js
+++ b/static/main.js
@@ -16,12 +16,14 @@
                     event.stopPropagation();
                 }
                 update_total_due();
+                update_paper_id_field();
                 form.classList.add('was-validated');
             }, false);
         });
     }, false);
     window.addEventListener('popstate', function(event) {
         update_total_due();
+        update_paper_id_field();
     }, false);
 })();
 
@@ -60,10 +62,10 @@
     var paper_id = $("#paper_id");
     if ($('#author').is(":checked")) {
         paper_id.removeAttr('disabled');
-        paper_id.attr('pattern', '\\d{1,4}');
+        paper_id.attr('pattern', '[1-9]\\d{0,3}');
         paper_id.attr('required', 'required');
         val = paper_id.val();
-        if (!x.match(/^\d{1,4}$/)) {
+        if (!val.match(/^\d{1,4}$/)) {
             paper_id.val('');
         }
     } else {
diff --git a/templates/register.htm b/templates/register.htm
index 3030101..200d46c 100644
--- a/templates/register.htm
+++ b/templates/register.htm
@@ -463,8 +463,8 @@
 
     <div class="form-outline col-md-5">
         <label class="form-label fw-bold" for="paper_id">Paper ID</label>
-        <input type="text" class="form-control fs-4" name="accepted_paper_id" id="paper_id" <?php echo isset($_POST[ 'author']) ? 'placeholder="0"' : 'disabled' ?> value="
-        <?php echo isset($_POST['paper_id']) ? htmlspecialchars($_POST['paper_id']) : '' ?>" />
+        <input type="text" class="form-control fs-4" name="accepted_paper_id" id="paper_id" <?php echo isset($_POST[ 'author']) ? 'placeholder="0" required' : 'disabled' ?>
+        <?php echo isset($_POST['accepted_paper_id']) ? 'value="'.htmlspecialchars($_POST['accepted_paper_id']) . '"' : '' ?> />
         <div class="invalid-feedback">
             Please provide the ID number of your accepted paper.
         </div>