Index: content-gallery.php
===================================================================
--- content-gallery.php	(revision 19933)
+++ content-gallery.php	(working copy)
@@ -37,7 +37,11 @@
 					if ( $images ) :
 						$total_images = count( $images );
 						$image = array_shift( $images );
-						$image_img_tag = wp_get_attachment_image( $image->ID, 'thumbnail' );
+						if ( has_post_thumbnail( $post->ID ) ) :
+							$image_img_tag = get_the_post_thumbnail( $post->ID, 'thumbnail' );
+						else :
+							$image_img_tag = wp_get_attachment_image( $image->ID, 'thumbnail' );
+						endif;
 				?>
 
 				<figure class="gallery-thumb">