diff --git a/install/css.php b/install/css.php
index f23e728f27c..3563a54bc97 100644
--- a/install/css.php
+++ b/install/css.php
@@ -372,6 +372,30 @@ body {
     background-color: rgb(245, 245, 245);
     padding: 8px 15px;
 }
+
+.w-100 {
+    width: 100%!important;
+}
+.flex-row-reverse {
+    flex-direction: row-reverse!important;
+}
+.btn-group, .btn-group-vertical {
+    position: relative;
+    display: inline-flex;
+    vertical-align: middle;
+}
+.mb-3, .my-3 {
+    margin-bottom: 1rem!important;
+}
+.mr-auto, .mx-auto {
+    margin-right: auto!important;
+}
+.ml-auto, .mx-auto {
+    margin-left: auto!important;
+}
+.ml-1, .mx-1 {
+    margin-left: .25rem!important;
+}
 /*
 End of MDL-43839 IE9 specific CSS.
 */
diff --git a/lib/installlib.php b/lib/installlib.php
index 3de940a9921..784af0847ca 100644
--- a/lib/installlib.php
+++ b/lib/installlib.php
@@ -385,9 +385,9 @@ function install_print_footer($config, $reload=false) {
     global $CFG;
 
     if ($config->stage > INSTALL_WELCOME) {
-        $first = '<input type="submit" id="previousbutton" name="previous" value="&laquo; '.s(get_string('previous')).'" />';
+        $first = '<input type="submit" id="previousbutton" class="btn btn-secondary ml-auto" name="previous" value="&laquo; '.s(get_string('previous')).'" />';
     } else {
-        $first = '<input type="submit" id="previousbutton" name="next" value="'.s(get_string('reload')).'" />';
+        $first = '<input type="submit" id="previousbutton" class="btn btn-secondary ml-auto" name="next" value="'.s(get_string('reload')).'" />';
         $first .= '<script type="text/javascript">
 //<![CDATA[
     var first = document.getElementById("previousbutton");
@@ -398,12 +398,12 @@ function install_print_footer($config, $reload=false) {
     }
 
     if ($reload) {
-        $next = '<input type="submit" id="nextbutton" class="btn btn-primary" name="next" value="'.s(get_string('reload')).'" />';
+        $next = '<input type="submit" id="nextbutton" class="btn btn-primary ml-1 mr-auto" name="next" value="'.s(get_string('reload')).'" />';
     } else {
-        $next = '<input type="submit" id="nextbutton" class="btn btn-primary" name="next" value="'.s(get_string('next')).' &raquo;" />';
+        $next = '<input type="submit" id="nextbutton" class="btn btn-primary ml-1 mr-auto" name="next" value="'.s(get_string('next')).' &raquo;" />';
     }
 
-    echo '</fieldset><fieldset id="nav_buttons">'.$first.$next.'</fieldset>';
+    echo '</fieldset><div id="nav_buttons" class="mb-3 btn-group w-100 flex-row-reverse">'.$next.$first.'</div>';
 
     $homelink  = '<div class="sitelink">'.
        '<a title="Moodle '. $CFG->target_release .'" href="http://docs.moodle.org/en/Administrator_documentation" onclick="this.target=\'_blank\'">'.