Index: wp-content/themes/twentythirteen/style.css
===================================================================
--- wp-content/themes/twentythirteen/style.css	(revision 24151)
+++ wp-content/themes/twentythirteen/style.css	(working copy)
@@ -738,6 +738,10 @@
 	margin: 5px auto;
 }
 
+img.alignnone {
+	margin: 5px 0;
+}
+
 .wp-caption .wp-caption-text,
 .entry-caption,
 .gallery-caption {
Index: wp-content/themes/twentythirteen/css/editor-style.css
===================================================================
--- wp-content/themes/twentythirteen/css/editor-style.css	(revision 24151)
+++ wp-content/themes/twentythirteen/css/editor-style.css	(working copy)
@@ -270,7 +270,11 @@
 	margin: 5px auto;
 }
 
+img.alignnone {
+	margin: 5px 0;
+}
 
+
 /**
  * Tables
  * ----------------------------------------------------------------------------