diff --git a/packages/vaadin-lumo-styles/utilities/accessibility.js b/packages/vaadin-lumo-styles/utilities/accessibility.js
index e11b7f64f4..abfab0cfb9 100644
--- a/packages/vaadin-lumo-styles/utilities/accessibility.js
+++ b/packages/vaadin-lumo-styles/utilities/accessibility.js
@@ -3,7 +3,7 @@
  * Copyright (c) 2017 - 2022 Vaadin Ltd.
  * This program is available under Apache License Version 2.0, available at https://vaadin.com/license/
  */
-import { css } from '@vaadin/vaadin-themable-mixin/register-styles';
+import { css } from '@vaadin/vaadin-themable-mixin/register-styles.js';
 
 export const accessibility = css`
   /* === Screen readers === */
diff --git a/packages/vaadin-lumo-styles/utilities/background.js b/packages/vaadin-lumo-styles/utilities/background.js
index 70dc024022..7727e2caad 100644
--- a/packages/vaadin-lumo-styles/utilities/background.js
+++ b/packages/vaadin-lumo-styles/utilities/background.js
@@ -3,7 +3,7 @@
  * Copyright (c) 2017 - 2022 Vaadin Ltd.
  * This program is available under Apache License Version 2.0, available at https://vaadin.com/license/
  */
-import { css } from '@vaadin/vaadin-themable-mixin/register-styles';
+import { css } from '@vaadin/vaadin-themable-mixin/register-styles.js';
 
 export const background = css`
   /* === Background color === */
diff --git a/packages/vaadin-lumo-styles/utilities/border.js b/packages/vaadin-lumo-styles/utilities/border.js
index 2f8518debf..9dc2ed9597 100644
--- a/packages/vaadin-lumo-styles/utilities/border.js
+++ b/packages/vaadin-lumo-styles/utilities/border.js
@@ -3,7 +3,7 @@
  * Copyright (c) 2017 - 2022 Vaadin Ltd.
  * This program is available under Apache License Version 2.0, available at https://vaadin.com/license/
  */
-import { css } from '@vaadin/vaadin-themable-mixin/register-styles';
+import { css } from '@vaadin/vaadin-themable-mixin/register-styles.js';
 
 export const border = css`
   /* === Border === */
diff --git a/packages/vaadin-lumo-styles/utilities/flexbox-grid.js b/packages/vaadin-lumo-styles/utilities/flexbox-grid.js
index 631399c6dc..7a2bc0cdac 100644
--- a/packages/vaadin-lumo-styles/utilities/flexbox-grid.js
+++ b/packages/vaadin-lumo-styles/utilities/flexbox-grid.js
@@ -3,7 +3,7 @@
  * Copyright (c) 2017 - 2022 Vaadin Ltd.
  * This program is available under Apache License Version 2.0, available at https://vaadin.com/license/
  */
-import { css } from '@vaadin/vaadin-themable-mixin/register-styles';
+import { css } from '@vaadin/vaadin-themable-mixin/register-styles.js';
 
 export const flexboxAndGrid = css`
   /* === Align content === */
diff --git a/packages/vaadin-lumo-styles/utilities/layout.js b/packages/vaadin-lumo-styles/utilities/layout.js
index 040c2633c2..adaa1d03b3 100644
--- a/packages/vaadin-lumo-styles/utilities/layout.js
+++ b/packages/vaadin-lumo-styles/utilities/layout.js
@@ -3,7 +3,7 @@
  * Copyright (c) 2017 - 2022 Vaadin Ltd.
  * This program is available under Apache License Version 2.0, available at https://vaadin.com/license/
  */
-import { css } from '@vaadin/vaadin-themable-mixin/register-styles';
+import { css } from '@vaadin/vaadin-themable-mixin/register-styles.js';
 
 export const layout = css`
   /* === Box sizing === */
diff --git a/packages/vaadin-lumo-styles/utilities/shadows.js b/packages/vaadin-lumo-styles/utilities/shadows.js
index 37f6373ea5..bd775f3678 100644
--- a/packages/vaadin-lumo-styles/utilities/shadows.js
+++ b/packages/vaadin-lumo-styles/utilities/shadows.js
@@ -3,7 +3,7 @@
  * Copyright (c) 2017 - 2022 Vaadin Ltd.
  * This program is available under Apache License Version 2.0, available at https://vaadin.com/license/
  */
-import { css } from '@vaadin/vaadin-themable-mixin/register-styles';
+import { css } from '@vaadin/vaadin-themable-mixin/register-styles.js';
 
 export const shadows = css`
   /* === Box shadows === */
diff --git a/packages/vaadin-lumo-styles/utilities/sizing.js b/packages/vaadin-lumo-styles/utilities/sizing.js
index eda12b101f..58a63e64b1 100644
--- a/packages/vaadin-lumo-styles/utilities/sizing.js
+++ b/packages/vaadin-lumo-styles/utilities/sizing.js
@@ -3,7 +3,7 @@
  * Copyright (c) 2017 - 2022 Vaadin Ltd.
  * This program is available under Apache License Version 2.0, available at https://vaadin.com/license/
  */
-import { css } from '@vaadin/vaadin-themable-mixin/register-styles';
+import { css } from '@vaadin/vaadin-themable-mixin/register-styles.js';
 
 export const sizing = css`
   /* === Height === */
diff --git a/packages/vaadin-lumo-styles/utilities/spacing.js b/packages/vaadin-lumo-styles/utilities/spacing.js
index 512a4e5e90..bf96c0f33c 100644
--- a/packages/vaadin-lumo-styles/utilities/spacing.js
+++ b/packages/vaadin-lumo-styles/utilities/spacing.js
@@ -3,7 +3,7 @@
  * Copyright (c) 2017 - 2022 Vaadin Ltd.
  * This program is available under Apache License Version 2.0, available at https://vaadin.com/license/
  */
-import { css } from '@vaadin/vaadin-themable-mixin/register-styles';
+import { css } from '@vaadin/vaadin-themable-mixin/register-styles.js';
 
 export const spacing = css`
   /* === Margin === */
diff --git a/packages/vaadin-lumo-styles/utilities/typography.js b/packages/vaadin-lumo-styles/utilities/typography.js
index 7be5d4af07..e1ada547a3 100644
--- a/packages/vaadin-lumo-styles/utilities/typography.js
+++ b/packages/vaadin-lumo-styles/utilities/typography.js
@@ -3,7 +3,7 @@
  * Copyright (c) 2017 - 2022 Vaadin Ltd.
  * This program is available under Apache License Version 2.0, available at https://vaadin.com/license/
  */
-import { css } from '@vaadin/vaadin-themable-mixin/register-styles';
+import { css } from '@vaadin/vaadin-themable-mixin/register-styles.js';
 
 export const typography = css`
   /* === Font size === */
diff --git a/packages/vaadin-lumo-styles/utility.js b/packages/vaadin-lumo-styles/utility.js
index b1f2b7a442..daf8f6e1af 100644
--- a/packages/vaadin-lumo-styles/utility.js
+++ b/packages/vaadin-lumo-styles/utility.js
@@ -3,7 +3,7 @@
  * Copyright (c) 2017 - 2022 Vaadin Ltd.
  * This program is available under Apache License Version 2.0, available at https://vaadin.com/license/
  */
-import { css, registerStyles } from '@vaadin/vaadin-themable-mixin/register-styles';
+import { css, registerStyles } from '@vaadin/vaadin-themable-mixin/register-styles.js';
 import { accessibility } from './utilities/accessibility.js';
 import { background } from './utilities/background.js';
 import { border } from './utilities/border.js';