Index: wp-content/themes/twentyseventeen/assets/css/editor-blocks.css
===================================================================
--- wp-content/themes/twentyseventeen/assets/css/editor-blocks.css	(revision 57139)
+++ wp-content/themes/twentyseventeen/assets/css/editor-blocks.css	(working copy)
@@ -818,3 +818,11 @@
 	margin-left: 0;
 	margin-right: 0;
 }
+
+.wp-block-cover[style*="font-size"] .wp-block-cover__inner-container .wp-block-heading,
+.wp-block-cover.has-small-font-size .wp-block-cover__inner-container .wp-block-heading,
+.wp-block-cover.has-large-font-size .wp-block-cover__inner-container .wp-block-heading,
+.wp-block-cover.has-medium-font-size-font-size .wp-block-cover__inner-container .wp-block-heading,
+.wp-block-cover.has-x-large-font-size.wp-block-cover__inner-container .wp-block-heading{
+    font-size: inherit;
+}
Index: wp-content/themes/twentyseventeen/style.css
===================================================================
--- wp-content/themes/twentyseventeen/style.css	(revision 57139)
+++ wp-content/themes/twentyseventeen/style.css	(working copy)
@@ -4371,3 +4371,11 @@
 		padding: 0;
 	}
 }
+
+.wp-block-cover[style*="font-size"] .wp-block-cover__inner-container .wp-block-heading,
+.wp-block-cover.has-small-font-size .wp-block-cover__inner-container .wp-block-heading,
+.wp-block-cover.has-large-font-size .wp-block-cover__inner-container .wp-block-heading,
+.wp-block-cover.has-medium-font-size-font-size .wp-block-cover__inner-container .wp-block-heading,
+.wp-block-cover.has-x-large-font-size.wp-block-cover__inner-container .wp-block-heading{
+    font-size: inherit;
+}