diff --git a/src/cards/ha-entities-card.js b/src/cards/ha-entities-card.js
index e3e4385084..ec213ca860 100644
--- a/src/cards/ha-entities-card.js
+++ b/src/cards/ha-entities-card.js
@@ -17,7 +17,7 @@ import LocalizeMixin from '../mixins/localize-mixin.js';
 class HaEntitiesCard extends LocalizeMixin(EventsMixin(PolymerElement)) {
   static get template() {
     return html`
-    <style is="custom-style" include="iron-flex"></style>
+    <style include="iron-flex"></style>
     <style>
       ha-card {
         padding: 16px;
diff --git a/src/components/ha-attributes.js b/src/components/ha-attributes.js
index b62986cdf6..9a2c860722 100644
--- a/src/components/ha-attributes.js
+++ b/src/components/ha-attributes.js
@@ -7,7 +7,7 @@ import hassAttributeUtil from '../util/hass-attributes-util.js';
 class HaAttributes extends PolymerElement {
   static get template() {
     return html`
-    <style is="custom-style" include="iron-flex iron-flex-alignment"></style>
+    <style include="iron-flex iron-flex-alignment"></style>
     <style>
       .data-entry .value {
         max-width: 200px;
diff --git a/src/components/ha-cards.js b/src/components/ha-cards.js
index 0b467123dc..4badec2d27 100644
--- a/src/components/ha-cards.js
+++ b/src/components/ha-cards.js
@@ -79,7 +79,7 @@ import getGroupEntities from '../common/entity/get_group_entities.js';
   class HaCards extends PolymerElement {
     static get template() {
       return html`
-    <style is="custom-style" include="iron-flex iron-flex-factors"></style>
+    <style include="iron-flex iron-flex-factors"></style>
     <style>
       :host {
         display: block;
diff --git a/src/components/ha-climate-control.js b/src/components/ha-climate-control.js
index 37df97fc42..380602e096 100644
--- a/src/components/ha-climate-control.js
+++ b/src/components/ha-climate-control.js
@@ -11,7 +11,7 @@ import EventsMixin from '../mixins/events-mixin.js';
 class HaClimateControl extends EventsMixin(PolymerElement) {
   static get template() {
     return html`
-    <style is="custom-style" include="iron-flex iron-flex-alignment"></style>
+    <style include="iron-flex iron-flex-alignment"></style>
     <style>
       /* local DOM styles go here */
       :host {
diff --git a/src/components/ha-cover-tilt-controls.js b/src/components/ha-cover-tilt-controls.js
index d69c960195..3c4625b90f 100644
--- a/src/components/ha-cover-tilt-controls.js
+++ b/src/components/ha-cover-tilt-controls.js
@@ -8,7 +8,7 @@ import CoverEntity from '../util/cover-model.js';
 class HaCoverTiltControls extends PolymerElement {
   static get template() {
     return html`
-    <style is="custom-style" include="iron-flex"></style>
+    <style include="iron-flex"></style>
     <style>
       :host {
         white-space: nowrap;
diff --git a/src/dialogs/more-info/controls/more-info-climate.js b/src/dialogs/more-info/controls/more-info-climate.js
index da9cffa72f..fd73f44720 100644
--- a/src/dialogs/more-info/controls/more-info-climate.js
+++ b/src/dialogs/more-info/controls/more-info-climate.js
@@ -22,7 +22,7 @@ import EventsMixin from '../../../mixins/events-mixin.js';
 class MoreInfoClimate extends EventsMixin(PolymerElement) {
   static get template() {
     return html`
-    <style is="custom-style" include="iron-flex"></style>
+    <style include="iron-flex"></style>
     <style>
       :host {
         color: var(--primary-text-color);
diff --git a/src/dialogs/more-info/controls/more-info-configurator.js b/src/dialogs/more-info/controls/more-info-configurator.js
index 2f50903f60..be579abb88 100644
--- a/src/dialogs/more-info/controls/more-info-configurator.js
+++ b/src/dialogs/more-info/controls/more-info-configurator.js
@@ -11,7 +11,7 @@ import '../../../components/ha-markdown.js';
 class MoreInfoConfigurator extends PolymerElement {
   static get template() {
     return html`
-    <style is="custom-style" include="iron-flex"></style>
+    <style include="iron-flex"></style>
     <style>
       p {
         margin: 8px 0;
diff --git a/src/dialogs/more-info/controls/more-info-cover.js b/src/dialogs/more-info/controls/more-info-cover.js
index 3edf437175..2f3bf08c66 100644
--- a/src/dialogs/more-info/controls/more-info-cover.js
+++ b/src/dialogs/more-info/controls/more-info-cover.js
@@ -17,7 +17,7 @@ import featureClassNames from '../../../common/entity/feature_class_names';
   class MoreInfoCover extends PolymerElement {
     static get template() {
       return html`
-    <style is="custom-style" include="iron-flex"></style>
+    <style include="iron-flex"></style>
     <style>
       .current_position, .tilt {
         max-height: 0px;
diff --git a/src/dialogs/more-info/controls/more-info-fan.js b/src/dialogs/more-info/controls/more-info-fan.js
index 0034c38f12..437022d793 100644
--- a/src/dialogs/more-info/controls/more-info-fan.js
+++ b/src/dialogs/more-info/controls/more-info-fan.js
@@ -19,7 +19,7 @@ import EventsMixin from '../../../mixins/events-mixin.js';
 class MoreInfoFan extends EventsMixin(PolymerElement) {
   static get template() {
     return html`
-    <style is="custom-style" include="iron-flex"></style>
+    <style include="iron-flex"></style>
     <style>
       .container-speed_list,
       .container-direction,
diff --git a/src/dialogs/more-info/controls/more-info-light.js b/src/dialogs/more-info/controls/more-info-light.js
index 140bc7fc75..f8d27b5a09 100644
--- a/src/dialogs/more-info/controls/more-info-light.js
+++ b/src/dialogs/more-info/controls/more-info-light.js
@@ -27,7 +27,7 @@ import EventsMixin from '../../../mixins/events-mixin.js';
   class MoreInfoLight extends EventsMixin(PolymerElement) {
     static get template() {
       return html`
-    <style is="custom-style" include="iron-flex"></style>
+    <style include="iron-flex"></style>
     <style>
       .effect_list {
         padding-bottom: 16px;
diff --git a/src/dialogs/more-info/controls/more-info-media_player.js b/src/dialogs/more-info/controls/more-info-media_player.js
index bbbedb8953..6da722cc5b 100644
--- a/src/dialogs/more-info/controls/more-info-media_player.js
+++ b/src/dialogs/more-info/controls/more-info-media_player.js
@@ -22,7 +22,7 @@ import EventsMixin from '../../../mixins/events-mixin.js';
   class MoreInfoMediaPlayer extends EventsMixin(PolymerElement) {
     static get template() {
       return html`
-    <style is="custom-style" include="iron-flex iron-flex-alignment"></style>
+    <style include="iron-flex iron-flex-alignment"></style>
     <style>
       .media-state {
         text-transform: capitalize;
diff --git a/src/dialogs/more-info/controls/more-info-script.js b/src/dialogs/more-info/controls/more-info-script.js
index 9075524927..c972572627 100644
--- a/src/dialogs/more-info/controls/more-info-script.js
+++ b/src/dialogs/more-info/controls/more-info-script.js
@@ -5,7 +5,7 @@ import { PolymerElement } from '@polymer/polymer/polymer-element.js';
 class MoreInfoScript extends PolymerElement {
   static get template() {
     return html`
-    <style is="custom-style" include="iron-flex iron-flex-alignment"></style>
+    <style include="iron-flex iron-flex-alignment"></style>
 
     <div class="layout vertical">
       <div class="data-entry layout justified horizontal">
diff --git a/src/dialogs/more-info/controls/more-info-sun.js b/src/dialogs/more-info/controls/more-info-sun.js
index 7287cacc2b..4e0fe88e2e 100644
--- a/src/dialogs/more-info/controls/more-info-sun.js
+++ b/src/dialogs/more-info/controls/more-info-sun.js
@@ -9,7 +9,7 @@ import formatTime from '../../../common/datetime/format_time.js';
 class MoreInfoSun extends PolymerElement {
   static get template() {
     return html`
-    <style is="custom-style" include="iron-flex iron-flex-alignment"></style>
+    <style include="iron-flex iron-flex-alignment"></style>
 
     <template is="dom-repeat" items="[[computeOrder(risingDate, settingDate)]]">
       <div class="data-entry layout justified horizontal">
diff --git a/src/dialogs/more-info/controls/more-info-vacuum.js b/src/dialogs/more-info/controls/more-info-vacuum.js
index ed36cae4a1..da84bfafbc 100644
--- a/src/dialogs/more-info/controls/more-info-vacuum.js
+++ b/src/dialogs/more-info/controls/more-info-vacuum.js
@@ -12,7 +12,7 @@ import '../../../components/ha-attributes.js';
 class MoreInfoVacuum extends PolymerElement {
   static get template() {
     return html`
-    <style is="custom-style" include="iron-flex iron-flex-alignment"></style>
+    <style include="iron-flex iron-flex-alignment"></style>
     <style>
       :host {
         @apply --paper-font-body1;
diff --git a/src/entrypoints/authorize.js b/src/entrypoints/authorize.js
index ed85f718ea..833732bfaa 100644
--- a/src/entrypoints/authorize.js
+++ b/src/entrypoints/authorize.js
@@ -10,7 +10,7 @@ import '../auth/ha-pick-auth-provider.js';
 class HaAuthorize extends PolymerElement {
   static get template() {
     return html`
-    <style is="custom-style" include="iron-flex iron-positioning"></style>
+    <style include="iron-flex iron-positioning"></style>
     <style>
       .layout {
         padding-top: 20px;
diff --git a/src/layouts/login-form.js b/src/layouts/login-form.js
index 48ccdff94f..4f1d7cb926 100644
--- a/src/layouts/login-form.js
+++ b/src/layouts/login-form.js
@@ -16,7 +16,7 @@ import LocalizeMixin from '../mixins/localize-mixin.js';
 class LoginForm extends LocalizeMixin(PolymerElement) {
   static get template() {
     return html`
-    <style is="custom-style" include="iron-flex iron-positioning"></style>
+    <style include="iron-flex iron-positioning"></style>
     <style>
       :host {
         white-space: nowrap;
diff --git a/src/panels/dev-event/ha-panel-dev-event.js b/src/panels/dev-event/ha-panel-dev-event.js
index 287d08518d..49fb844e07 100644
--- a/src/panels/dev-event/ha-panel-dev-event.js
+++ b/src/panels/dev-event/ha-panel-dev-event.js
@@ -19,7 +19,7 @@ import EventsMixin from '../../mixins/events-mixin.js';
 class HaPanelDevEvent extends EventsMixin(PolymerElement) {
   static get template() {
     return html`
-    <style is="custom-style" include="ha-style iron-flex iron-positioning"></style>
+    <style include="ha-style iron-flex iron-positioning"></style>
     <style>
       :host {
         -ms-user-select: initial;
diff --git a/src/panels/dev-template/ha-panel-dev-template.js b/src/panels/dev-template/ha-panel-dev-template.js
index 972169aa57..a8e9180953 100644
--- a/src/panels/dev-template/ha-panel-dev-template.js
+++ b/src/panels/dev-template/ha-panel-dev-template.js
@@ -14,7 +14,7 @@ import '../../resources/ha-style.js';
 class HaPanelDevTemplate extends PolymerElement {
   static get template() {
     return html`
-    <style is="custom-style" include="ha-style iron-flex iron-positioning"></style>
+    <style include="ha-style iron-flex iron-positioning"></style>
     <style>
       :host {
         -ms-user-select: initial;
diff --git a/src/panels/logbook/ha-logbook.js b/src/panels/logbook/ha-logbook.js
index 18ea2df829..53419fe8e6 100644
--- a/src/panels/logbook/ha-logbook.js
+++ b/src/panels/logbook/ha-logbook.js
@@ -14,7 +14,7 @@ import EventsMixin from '../../mixins/events-mixin.js';
 class HaLogbook extends EventsMixin(PolymerElement) {
   static get template() {
     return html`
-    <style is="custom-style" include="iron-flex"></style>
+    <style include="iron-flex"></style>
     <style>
       :host {
         display: block;
diff --git a/src/panels/map/ha-entity-marker.js b/src/panels/map/ha-entity-marker.js
index 3ff8b2e7ab..6e661c0fcd 100644
--- a/src/panels/map/ha-entity-marker.js
+++ b/src/panels/map/ha-entity-marker.js
@@ -10,7 +10,7 @@ import EventsMixin from '../../mixins/events-mixin.js';
 class HaEntityMarker extends EventsMixin(PolymerElement) {
   static get template() {
     return html`
-    <style is="custom-style" include="iron-positioning"></style>
+    <style include="iron-positioning"></style>
     <style>
     .marker {
       vertical-align: top;
diff --git a/src/resources/ha-style.js b/src/resources/ha-style.js
index 058b2dae28..2248c62efc 100644
--- a/src/resources/ha-style.js
+++ b/src/resources/ha-style.js
@@ -5,7 +5,7 @@ const documentContainer = document.createElement('template');
 documentContainer.setAttribute('style', 'display: none;');
 
 documentContainer.innerHTML = `<custom-style>
-  <style is="custom-style">/* remove is= on Polymer 2 */
+  <style>
     /*
       Home Assistant default styles.
 
diff --git a/src/state-summary/state-card-climate.js b/src/state-summary/state-card-climate.js
index 51535473f8..2670ac9e67 100644
--- a/src/state-summary/state-card-climate.js
+++ b/src/state-summary/state-card-climate.js
@@ -8,7 +8,7 @@ import '../components/ha-climate-state.js';
 class StateCardClimate extends PolymerElement {
   static get template() {
     return html`
-    <style is="custom-style" include="iron-flex iron-flex-alignment"></style>
+    <style include="iron-flex iron-flex-alignment"></style>
     <style>
       :host {
         @apply --paper-font-body1;
diff --git a/src/state-summary/state-card-configurator.js b/src/state-summary/state-card-configurator.js
index 936e0c1f7f..e58c4e3565 100644
--- a/src/state-summary/state-card-configurator.js
+++ b/src/state-summary/state-card-configurator.js
@@ -8,7 +8,7 @@ import '../components/entity/state-info.js';
 class StateCardConfigurator extends PolymerElement {
   static get template() {
     return html`
-    <style is="custom-style" include="iron-flex iron-flex-alignment"></style>
+    <style include="iron-flex iron-flex-alignment"></style>
     <style>
       paper-button {
         color: var(--primary-color);
diff --git a/src/state-summary/state-card-cover.js b/src/state-summary/state-card-cover.js
index dbc3fbcfb7..1ea2eb3bf0 100644
--- a/src/state-summary/state-card-cover.js
+++ b/src/state-summary/state-card-cover.js
@@ -10,7 +10,7 @@ import CoverEntity from '../util/cover-model.js';
 class StateCardCover extends PolymerElement {
   static get template() {
     return html`
-    <style is="custom-style" include="iron-flex iron-flex-alignment"></style>
+    <style include="iron-flex iron-flex-alignment"></style>
     <style>
       :host {
         line-height: 1.5;
diff --git a/src/state-summary/state-card-input_number.js b/src/state-summary/state-card-input_number.js
index 6941fc3250..d8011ba1f6 100644
--- a/src/state-summary/state-card-input_number.js
+++ b/src/state-summary/state-card-input_number.js
@@ -13,7 +13,7 @@ class StateCardInputNumber extends mixinBehaviors([
 ], PolymerElement) {
   static get template() {
     return html`
-    <style is="custom-style" include="iron-flex iron-flex-alignment"></style>
+    <style include="iron-flex iron-flex-alignment"></style>
     <style>
       paper-slider {
         margin-left: auto;
diff --git a/src/state-summary/state-card-input_text.js b/src/state-summary/state-card-input_text.js
index a4b05a6c7c..6dcc6e4ebf 100644
--- a/src/state-summary/state-card-input_text.js
+++ b/src/state-summary/state-card-input_text.js
@@ -8,7 +8,7 @@ import '../components/entity/state-info.js';
 class StateCardInputText extends PolymerElement {
   static get template() {
     return html`
-    <style is="custom-style" include="iron-flex iron-flex-alignment"></style>
+    <style include="iron-flex iron-flex-alignment"></style>
     <style>
       paper-input {
         margin-left: 16px;
diff --git a/src/state-summary/state-card-media_player.js b/src/state-summary/state-card-media_player.js
index 8dbcb8821f..2d2bc3b1d2 100644
--- a/src/state-summary/state-card-media_player.js
+++ b/src/state-summary/state-card-media_player.js
@@ -12,7 +12,7 @@ import HassMediaPlayerEntity from '../util/hass-media-player-model.js';
 class StateCardMediaPlayer extends LocalizeMixin(PolymerElement) {
   static get template() {
     return html`
-    <style is="custom-style" include="iron-flex iron-flex-alignment"></style>
+    <style include="iron-flex iron-flex-alignment"></style>
     <style>
       :host {
         line-height: 1.5;
diff --git a/src/state-summary/state-card-scene.js b/src/state-summary/state-card-scene.js
index 34d17f386b..2bfcca15b5 100644
--- a/src/state-summary/state-card-scene.js
+++ b/src/state-summary/state-card-scene.js
@@ -12,7 +12,7 @@ import LocalizeMixin from '../mixins/localize-mixin.js';
 class StateCardScene extends LocalizeMixin(PolymerElement) {
   static get template() {
     return html`
-    <style is="custom-style" include="iron-flex iron-flex-alignment"></style>
+    <style include="iron-flex iron-flex-alignment"></style>
     <style>
       paper-button {
         color: var(--primary-color);
diff --git a/src/state-summary/state-card-script.js b/src/state-summary/state-card-script.js
index 8ef55a9860..889c5dfe44 100644
--- a/src/state-summary/state-card-script.js
+++ b/src/state-summary/state-card-script.js
@@ -14,7 +14,7 @@ import LocalizeMixin from '../mixins/localize-mixin.js';
 class StateCardScript extends LocalizeMixin(PolymerElement) {
   static get template() {
     return html`
-    <style is="custom-style" include="iron-flex iron-flex-alignment"></style>
+    <style include="iron-flex iron-flex-alignment"></style>
     <style>
       paper-button {
         color: var(--primary-color);
diff --git a/src/state-summary/state-card-timer.js b/src/state-summary/state-card-timer.js
index 3e908ce0d4..e430c7d766 100644
--- a/src/state-summary/state-card-timer.js
+++ b/src/state-summary/state-card-timer.js
@@ -15,7 +15,7 @@ import LocalizeMixin from '../mixins/localize-mixin.js';
 class StateCardTimer extends LocalizeMixin(PolymerElement) {
   static get template() {
     return html`
-    <style is="custom-style" include="iron-flex iron-flex-alignment"></style>
+    <style include="iron-flex iron-flex-alignment"></style>
     <style>
       .state {
         @apply --paper-font-body1;
diff --git a/src/state-summary/state-card-toggle.js b/src/state-summary/state-card-toggle.js
index 40e1711589..5eb44f935c 100644
--- a/src/state-summary/state-card-toggle.js
+++ b/src/state-summary/state-card-toggle.js
@@ -8,7 +8,7 @@ import '../components/entity/state-info.js';
 class StateCardToggle extends PolymerElement {
   static get template() {
     return html`
-    <style is="custom-style" include="iron-flex iron-flex-alignment"></style>
+    <style include="iron-flex iron-flex-alignment"></style>
     <style>
       ha-entity-toggle {
         margin: -4px -16px -4px 0;