diff --git a/group/clientlib.js b/group/clientlib.js
index 9e433a196c4..9bdb2bc8f80 100644
--- a/group/clientlib.js
+++ b/group/clientlib.js
@@ -169,7 +169,7 @@ UpdatableMembersCombo.prototype.refreshMembers = function () {
     document.getElementById("deletegroup").disabled = selectionCount == 0;
 
     if(singleSelection) {
-        var sUrl = this.wwwRoot+"/group/index.php?id="+this.courseId+"&group="+groupId+"&act_ajax_getmembersingroup";
+        var sUrl = this.wwwRoot + "/group/index.php?id=" + this.courseId + "&group=" + groupId + "&action=ajax_getmembersingroup";
         var self = this;
         YUI().use('io', function (Y) {
             Y.io(sUrl, {
diff --git a/group/index.php b/group/index.php
index ce3fd9e9d1a..b291c396eed 100644
--- a/group/index.php
+++ b/group/index.php
@@ -28,7 +28,8 @@ require_once('lib.php');
 $courseid = required_param('id', PARAM_INT);
 $groupid  = optional_param('group', false, PARAM_INT);
 $userid   = optional_param('user', false, PARAM_INT);
-$action   = groups_param_action();
+$action = optional_param('action', false, PARAM_TEXT);
+
 // Support either single group= parameter, or array groups[].
 if ($groupid) {
     $groupids = array($groupid);
@@ -249,35 +250,3 @@ $output = $PAGE->get_renderer('core_group');
 echo $output->render($renderable);
 
 echo $OUTPUT->footer();
-
-/**
- * Returns the first button action with the given prefix, taken from
- * POST or GET, otherwise returns false.
- * @see /lib/moodlelib.php function optional_param().
- * @param string $prefix 'act_' as in 'action'.
- * @return string The action without the prefix, or false if no action found.
- */
-function groups_param_action($prefix = 'act_') {
-    $action = false;
-
-    if ($_POST) {
-        $formvars = $_POST;
-    } else if ($_GET) {
-        $formvars = $_GET;
-    }
-
-    if ($formvars) {
-        foreach ($formvars as $key => $value) {
-            if (preg_match("/$prefix(.+)/", $key, $matches)) {
-                $action = $matches[1];
-                break;
-            }
-        }
-    }
-    if ($action && !preg_match('/^\w+$/', $action)) {
-        $action = false;
-        throw new \moodle_exception('unknowaction');
-    }
-
-    return $action;
-}
diff --git a/group/templates/index.mustache b/group/templates/index.mustache
index 4a5b4d13220..ae9851ab463 100644
--- a/group/templates/index.mustache
+++ b/group/templates/index.mustache
@@ -92,22 +92,22 @@
                     </select>
                 </div>
                 <div class="form-group">
-                    <input type="submit" name="act_updatemembers" id="updatemembers" value="{{#str}}showmembersforgroup, group{{/str}}" class="btn btn-secondary" />
+                    <button type="submit" name="action" id="updatemembers" value="updatemembers" class="btn btn-secondary">{{#str}}showmembersforgroup, group{{/str}}</button>
                 </div>
                 <div class="form-group">
-                    <input type="submit" name="act_showgroupsettingsform" id="showeditgroupsettingsform" value="{{#str}}editgroupsettings, group{{/str}}" {{#editgroupsettingsdisabled}}disabled="disabled"{{/editgroupsettingsdisabled}} class="btn btn-secondary" />
+                    <button type="submit" name="action" id="showeditgroupsettingsform" value="showgroupsettingsform" {{#editgroupsettingsdisabled}}disabled="disabled"{{/editgroupsettingsdisabled}} class="btn btn-secondary">{{#str}}editgroupsettings, group{{/str}}</button>
                 </div>
                 <div class="form-group">
-                    <input type="submit" name="act_deletegroup" id="deletegroup" value="{{#str}}deleteselectedgroup, group{{/str}}" {{#deletegroupdisabled}}disabled="disabled"{{/deletegroupdisabled}} class="btn btn-secondary" />
+                    <button type="submit" name="action" id="deletegroup" value="deletegroup" {{#deletegroupdisabled}}disabled="disabled"{{/deletegroupdisabled}} class="btn btn-secondary">{{#str}}deleteselectedgroup, group{{/str}}</button>
                 </div>
                 <div class="form-group">
-                    <input type="submit" name="act_showcreateorphangroupform" id="showcreateorphangroupform" value="{{#str}}creategroup, group{{/str}}" class="btn btn-secondary" />
+                    <button type="submit" name="action" id="showcreateorphangroupform" value="showcreateorphangroupform" class="btn btn-secondary">{{#str}}creategroup, group{{/str}}</button>
                 </div>
                 <div class="form-group">
-                    <input type="submit" name="act_showautocreategroupsform" id="showautocreategroupsform" value="{{#str}}autocreategroups, group{{/str}}" class="btn btn-secondary" />
+                    <button type="submit" name="action" id="showautocreategroupsform" value="showautocreategroupsform" class="btn btn-secondary">{{#str}}autocreategroups, group{{/str}}</button>
                 </div>
                 <div class="form-group">
-                    <input type="submit" name="act_showimportgroups" id="showimportgroups" value="{{#str}}importgroups, group{{/str}}" class="btn btn-secondary" />
+                    <button type="submit" name="action" id="showimportgroups" value="showimportgroups" class="btn btn-secondary">{{#str}}importgroups, group{{/str}}</button>
                 </div>
             </div>
             <div class="col-md-6 mb-1">
@@ -127,7 +127,7 @@
                     </select>
                 </div>
                 <div class="form-group">
-                    <input type="submit" value="{{#str}}adduserstogroup, group{{/str}}" class="btn btn-secondary" {{#addmembersdisabled}}disabled="disabled"{{/addmembersdisabled}} name="act_showaddmembersform" id="showaddmembersform"/>
+                    <button type="submit" value="showaddmembersform" class="btn btn-secondary" {{#addmembersdisabled}}disabled="disabled"{{/addmembersdisabled}} name="action" id="showaddmembersform">{{#str}}adduserstogroup, group{{/str}}</button>
                 </div>
             </div>
         </div>