Index: themes/twentythirteen/css/editor-blocks.css
===================================================================
--- themes/twentythirteen/css/editor-blocks.css	(revision 53231)
+++ themes/twentythirteen/css/editor-blocks.css	(working copy)
@@ -161,6 +161,9 @@
 .rtl .editor-block-list__block table td {
 	text-align: right;
 }
+.editor-styles-wrapper table {
+	font-size: inherit;
+}
 
 /* Code */
 
Index: themes/twentythirteen/style.css
===================================================================
--- themes/twentythirteen/style.css	(revision 53231)
+++ themes/twentythirteen/style.css	(working copy)
@@ -420,7 +420,7 @@
 	border-bottom: 1px solid #ededed;
 	border-collapse: collapse;
 	border-spacing: 0;
-	font-size: 14px;
+	font-size: inherit;
 	line-height: 2;
 	margin: 0 0 20px;
 	width: 100%;