diff --git a/app/assets/javascripts/discourse/app/components/emoji-picker.hbs b/app/assets/javascripts/discourse/app/components/emoji-picker.hbs
index 363e2120bd7..00445a9a147 100644
--- a/app/assets/javascripts/discourse/app/components/emoji-picker.hbs
+++ b/app/assets/javascripts/discourse/app/components/emoji-picker.hbs
@@ -11,7 +11,7 @@
           {{on "click" (fn this.onCategorySelection "recent")}}
           data-section="recent"
           type="button"
-          class="btn btn-default category-button emoji"
+          class="btn btn-flat category-button emoji"
         >
           {{replace-emoji ":star:"}}
         </button>
diff --git a/app/assets/javascripts/discourse/app/templates/preferences/interface.hbs b/app/assets/javascripts/discourse/app/templates/preferences/interface.hbs
index 95c5dce5334..f77067fb291 100644
--- a/app/assets/javascripts/discourse/app/templates/preferences/interface.hbs
+++ b/app/assets/javascripts/discourse/app/templates/preferences/interface.hbs
@@ -247,7 +247,7 @@
     <DButton
       @action={{action "resetSeenUserTips"}}
       data-setting-name="user-reset-seen-user-tips"
-      class="pref-reset-seen-user-tips"
+      class="btn-default pref-reset-seen-user-tips"
     >{{i18n "user.reset_seen_user_tips"}}</DButton>
   {{/if}}
 </fieldset>
diff --git a/app/assets/javascripts/discourse/app/templates/user-invited-show.hbs b/app/assets/javascripts/discourse/app/templates/user-invited-show.hbs
index 549adaa10e4..33584ca6a66 100644
--- a/app/assets/javascripts/discourse/app/templates/user-invited-show.hbs
+++ b/app/assets/javascripts/discourse/app/templates/user-invited-show.hbs
@@ -21,7 +21,7 @@
           @icon="plus"
           @action={{this.createInvite}}
           @label="user.invited.create"
-          class="btn-default"
+          class="btn-flat"
         />
         {{#if this.canBulkInvite}}
           {{#if this.siteSettings.allow_bulk_invite}}
diff --git a/app/assets/javascripts/select-kit/addon/components/notifications-filter/notifications-filter-header.js b/app/assets/javascripts/select-kit/addon/components/notifications-filter/notifications-filter-header.js
index 30f3a50a24a..442adf3c952 100644
--- a/app/assets/javascripts/select-kit/addon/components/notifications-filter/notifications-filter-header.js
+++ b/app/assets/javascripts/select-kit/addon/components/notifications-filter/notifications-filter-header.js
@@ -3,7 +3,7 @@ import discourseComputed from "discourse-common/utils/decorators";
 import DropdownSelectBoxHeaderComponent from "select-kit/components/dropdown-select-box/dropdown-select-box-header";
 
 export default DropdownSelectBoxHeaderComponent.extend({
-  classNames: ["notifications-filter-header"],
+  classNames: ["notifications-filter-header", "btn-flat"],
   label: fmt("value", "user.user_notifications.filters.%@"),
 
   @discourseComputed("selectKit.isExpanded")