diff --git a/lib/form/templates/element-group.mustache b/lib/form/templates/element-group.mustache
index 67d7866eeed..208dd6d0d14 100644
--- a/lib/form/templates/element-group.mustache
+++ b/lib/form/templates/element-group.mustache
@@ -7,17 +7,27 @@
         {{/element.hiddenlabel}}
     {{/label}}
     {{$element}}
-        <fieldset class="w-100 m-0 p-0 border-0">
-            {{#label}}
+        {{#label}}
+            <fieldset class="w-100 m-0 p-0 border-0">
                 <legend class="sr-only">{{label}}</legend>
-            {{/label}}
-            <div class="d-flex flex-wrap align-items-center">
-            {{#element.elements}}
-                {{{separator}}}
-                {{{html}}}
-            {{/element.elements}}
+                <div class="d-flex flex-wrap align-items-center">
+                {{#element.elements}}
+                    {{{separator}}}
+                    {{{html}}}
+                {{/element.elements}}
+                </div>
+            </fieldset>
+        {{/label}}
+        {{^label}}
+            <div class="w-100 m-0 p-0 border-0">
+                <div class="d-flex flex-wrap align-items-center">
+                {{#element.elements}}
+                    {{{separator}}}
+                    {{{html}}}
+                {{/element.elements}}
+                </div>
             </div>
-        </fieldset>
+        {{/label}}
     {{/element}}
 {{/ core_form/element-template }}
 {{#js}}
diff --git a/theme/upgrade.txt b/theme/upgrade.txt
index d7f16177da5..5610a75127d 100644
--- a/theme/upgrade.txt
+++ b/theme/upgrade.txt
@@ -5,6 +5,7 @@ information provided here is intended especially for theme designer.
 * Theme selection is now performed using cards and modals.
 * The 'choosereadme' string for each theme is expected to be plain text. HTML content will not render when displayed in the modal.
 * Theme selector page has been moved to admin/themeselector.php (previously theme/index.php)
+* Moodleforms no longer use tag 'fieldset' for groups without labels (legends). Avoid targeting tag 'fieldset' in the theme CSS.
 
 === 4.3 ===
 * The core_renderer::htmllize_file_tree method has been deprecated. This was missed before Moodle 2.0.