Index: wp-content/themes/twentythirteen/style.css
===================================================================
--- wp-content/themes/twentythirteen/style.css	(revision 23592)
+++ wp-content/themes/twentythirteen/style.css	(working copy)
@@ -746,7 +746,8 @@
 }
 
 .wp-caption .wp-caption-text,
-.entry-caption {
+.entry-caption,
+.gallery-caption {
 	color: #220e10;
 	font-size: 18px;
 	font-style: italic;
@@ -1336,14 +1337,8 @@
 }
 
 .gallery-caption {
-	color: #777;
-	font-size: 14px;
-	font-style: italic;
-	padding-top: 4px;
-}
-
-.gallery-caption {
-	width: 90%;
+	margin-bottom: 0;
+	text-align: left;
 }