diff --git a/modules/mobile/notificationsFilterOverlay.less b/modules/mobile/notificationsFilterOverlay.less
index ae06d2542..96afc1d7d 100644
--- a/modules/mobile/notificationsFilterOverlay.less
+++ b/modules/mobile/notificationsFilterOverlay.less
@@ -1,5 +1,4 @@
 @import 'mediawiki.ui/variables.less';
-@import 'mediawiki.mixins.less';
 
 .notifications-filter-overlay {
 	padding-top: 0;
@@ -19,7 +18,7 @@
 		padding-bottom: 0;
 
 		.mw-echo-ui-pageNotificationsOptionWidget {
-			.box-sizing( border-box );
+			box-sizing: border-box;
 			border: 1px solid @colorGray12;
 			padding: 0.7em 1.5em 1em 1em;
 			width: 100%;
diff --git a/modules/nojs/mw.echo.badge.less b/modules/nojs/mw.echo.badge.less
index e8df8bd92..55ecdc40b 100644
--- a/modules/nojs/mw.echo.badge.less
+++ b/modules/nojs/mw.echo.badge.less
@@ -1,5 +1,4 @@
 @import '../echo.variables.less';
-@import 'mediawiki.mixins.less';
 
 /* stylelint-disable no-descending-specificity */
 /* We have to include the #pt-notifications selector due to monobook */
@@ -8,6 +7,7 @@
 	#pt-notifications-notice & {
 		position: relative;
 		display: block;
+		box-sizing: border-box;
 		width: 20px;
 		height: 20px;
 		margin: 0 2px;
@@ -19,7 +19,6 @@
 		cursor: pointer;
 		text-decoration: none;
 		line-height: normal;
-		.box-sizing( border-box );
 		opacity: 0.87;
 		color: transparent;
 
diff --git a/modules/nojs/mw.echo.notifications.less b/modules/nojs/mw.echo.notifications.less
index 8defd1044..b09527cff 100644
--- a/modules/nojs/mw.echo.notifications.less
+++ b/modules/nojs/mw.echo.notifications.less
@@ -6,8 +6,8 @@
 // where the formatting of the notifications include the following structure
 .mw-echo-state {
 	display: block;
+	box-sizing: border-box;
 	width: 100%;
-	.box-sizing( border-box );
 
 	.mw-echo-notification-primary-link {
 		display: none;
diff --git a/modules/styles/mw.echo.ui.NotificationBadgeWidget.less b/modules/styles/mw.echo.ui.NotificationBadgeWidget.less
index 0a960c588..2bd899e52 100644
--- a/modules/styles/mw.echo.ui.NotificationBadgeWidget.less
+++ b/modules/styles/mw.echo.ui.NotificationBadgeWidget.less
@@ -7,7 +7,7 @@
 	&-popup {
 		> .oo-ui-popupWidget-popup {
 			> .oo-ui-popupWidget-head {
-				.box-sizing( border-box );
+				box-sizing: border-box;
 				height: 3.1428571em; // = 44px as result of 44 / 16 (font-size browser) / 0.875 (OOUI WikimediaUI theme font-size)
 				border-bottom: 1px solid #c8ccd1;
 				margin: 0;
@@ -67,7 +67,7 @@
 						display: table-cell;
 						white-space: normal;
 						width: @notification-popup-width / 2;
-						.box-sizing( border-box );
+						box-sizing: border-box;
 
 						&:last-child {
 							border-left: 1px solid #c8ccd1;
diff --git a/modules/styles/mw.echo.ui.NotificationItemWidget.less b/modules/styles/mw.echo.ui.NotificationItemWidget.less
index 0dd784093..2a7d2a5df 100644
--- a/modules/styles/mw.echo.ui.NotificationItemWidget.less
+++ b/modules/styles/mw.echo.ui.NotificationItemWidget.less
@@ -8,7 +8,7 @@
 	position: relative;
 	white-space: normal;
 	padding: 0.8em 1em 0.5em 1em;
-	.box-sizing( border-box );
+	box-sizing: border-box;
 	border: 1px solid #c8ccd1;
 	border-bottom: 0;
 
@@ -74,10 +74,10 @@
 
 	&-content {
 		display: block;
+		box-sizing: border-box;
 		// The icon is 30px
 		margin-left: 30px;
 		padding-left: 0.8em;
-		.box-sizing( border-box );
 
 		&-message {
 			line-height: 1.3em;
diff --git a/modules/styles/mw.echo.ui.PageNotificationsOptionWidget.less b/modules/styles/mw.echo.ui.PageNotificationsOptionWidget.less
index 44d51b455..2fc837cb9 100644
--- a/modules/styles/mw.echo.ui.PageNotificationsOptionWidget.less
+++ b/modules/styles/mw.echo.ui.PageNotificationsOptionWidget.less
@@ -3,8 +3,8 @@
 
 .mw-echo-ui-pageNotificationsOptionWidget {
 	clear: both;
+	box-sizing: border-box;
 	width: 100%;
-	.box-sizing( border-box );
 
 	&.oo-ui-optionWidget {
 		.transition( ~'background-color 100ms, color 100ms' );
diff --git a/modules/styles/mw.echo.ui.ToggleReadCircleButtonWidget.less b/modules/styles/mw.echo.ui.ToggleReadCircleButtonWidget.less
index 7dc5692c7..b64515777 100644
--- a/modules/styles/mw.echo.ui.ToggleReadCircleButtonWidget.less
+++ b/modules/styles/mw.echo.ui.ToggleReadCircleButtonWidget.less
@@ -1,15 +1,14 @@
-@import 'mediawiki.mixins.less';
 @import '../echo.variables.less';
 
 .mw-echo-ui-toggleReadCircleButtonWidget {
 	&-circle {
 		border-radius: 50%;
+		box-sizing: border-box;
 		min-width: 10px;
 		width: @bundle-group-padding;
 		min-height: 10px;
 		height: @bundle-group-padding;
 		margin: @bundle-group-padding;
-		.box-sizing( border-box );
 
 		// Mark as read
 		background-color: #36c;