Index: src/wp-admin/includes/class-custom-background.php
===================================================================
--- src/wp-admin/includes/class-custom-background.php	(revision 51499)
+++ src/wp-admin/includes/class-custom-background.php	(working copy)
@@ -418,7 +418,7 @@
 	<div class="button-group">
 				<?php foreach ( $group as $value => $input ) : ?>
 		<label>
-			<input class="screen-reader-text" name="background-position" type="radio" value="<?php echo esc_attr( $value ); ?>"<?php checked( $value, $background_position ); ?>>
+			<input class="ui-helper-hidden-accessible" name="background-position" type="radio" value="<?php echo esc_attr( $value ); ?>"<?php checked( $value, $background_position ); ?>>
 			<span class="button display-options position"><span class="<?php echo esc_attr( $input['icon'] ); ?>" aria-hidden="true"></span></span>
 			<span class="screen-reader-text"><?php echo $input['label']; ?></span>
 		</label>
Index: src/wp-includes/customize/class-wp-customize-background-position-control.php
===================================================================
--- src/wp-includes/customize/class-wp-customize-background-position-control.php	(revision 51499)
+++ src/wp-includes/customize/class-wp-customize-background-position-control.php	(working copy)
@@ -96,7 +96,7 @@
 					<div class="button-group">
 					<?php foreach ( $group as $value => $input ) : ?>
 						<label>
-							<input class="screen-reader-text" name="background-position" type="radio" value="<?php echo esc_attr( $value ); ?>">
+							<input class="ui-helper-hidden-accessible" name="background-position" type="radio" value="<?php echo esc_attr( $value ); ?>">
 							<span class="button display-options position"><span class="<?php echo esc_attr( $input['icon'] ); ?>" aria-hidden="true"></span></span>
 							<span class="screen-reader-text"><?php echo $input['label']; ?></span>
 						</label>