Index: wp-includes/vars.php
===================================================================
--- wp-includes/vars.php	(revision 20971)
+++ wp-includes/vars.php	(working copy)
@@ -113,6 +113,8 @@
 		$is_mobile = false;
 	} elseif ( strpos($_SERVER['HTTP_USER_AGENT'], 'Mobile') !== false // many mobile devices (all iPhone, iPad, etc.)
 		|| strpos($_SERVER['HTTP_USER_AGENT'], 'Android') !== false
+		|| strpos($_SERVER['HTTP_USER_AGENT'], 'Silk/') !== false
+		|| strpos($_SERVER['HTTP_USER_AGENT'], 'Kindle') !== false
 		|| strpos($_SERVER['HTTP_USER_AGENT'], 'BlackBerry') !== false
 		|| strpos($_SERVER['HTTP_USER_AGENT'], 'Opera Mini') !== false ) {
 			$is_mobile = true;