Index: wp-includes/kses.php
===================================================================
--- wp-includes/kses.php	(revision 6597)
+++ wp-includes/kses.php	(working copy)
@@ -318,8 +318,11 @@
 	# Is there a closing XHTML slash at the end of the attributes?
 
 	$xhtml_slash = '';
-	if (preg_match('%\s/\s*$%', $attr))
+	if (preg_match('%(\s?)/\s*$%', $attr, $match)) {
 		$xhtml_slash = ' /';
+		if ( '' == $match[1] )
+			$attr = rtrim($attr, '/ ') . ' /';
+	}
 
 	# Are any attributes allowed at all for this element?