Index: wp-includes/pluggable.php
===================================================================
--- wp-includes/pluggable.php	(revision 21206)
+++ wp-includes/pluggable.php	(working copy)
@@ -1627,14 +1627,7 @@
 	if ( !empty($email) )
 		$email_hash = md5( strtolower( trim( $email ) ) );
 
-	if ( is_ssl() ) {
-		$host = 'https://secure.gravatar.com';
-	} else {
-		if ( !empty($email) )
-			$host = sprintf( "http://%d.gravatar.com", ( hexdec( $email_hash[0] ) % 2 ) );
-		else
-			$host = 'http://0.gravatar.com';
-	}
+	$host = '//gravatar.com';
 
 	if ( 'mystery' == $default )
 		$default = "$host/avatar/ad516503a11cd5ca435acc9bb6523536?s={$size}"; // ad516503a11cd5ca435acc9bb6523536 == md5('unknown@gravatar.com')