Index: wp-admin/includes/theme-install.php
===================================================================
--- wp-admin/includes/theme-install.php	(revision 22136)
+++ wp-admin/includes/theme-install.php	(working copy)
@@ -138,7 +138,8 @@
 <p class="install-help"><?php _e('If you have a theme in a .zip format, you may install it by uploading it here.') ?></p>
 <form method="post" enctype="multipart/form-data" action="<?php echo self_admin_url('update.php?action=upload-theme') ?>">
 	<?php wp_nonce_field( 'theme-upload') ?>
-	<input type="file" name="themezip" />
+	<label class="screen-reader-text" for="themezip"><?php _e('Theme zip file'); ?></label>
+	<input type="file" id="themezip" name="themezip" />
 	<?php submit_button( __( 'Install Now' ), 'button', 'install-theme-submit', false ); ?>
 </form>
 	<?php