diff --git a/src/wp-includes/js/mce-view.js b/src/wp-includes/js/mce-view.js
index 1fd477c8a3..d3af61ee53 100644
--- a/src/wp-includes/js/mce-view.js
+++ b/src/wp-includes/js/mce-view.js
@@ -289,10 +289,12 @@ window.wp = window.wp || {};
 					attachments = this.attachments.toJSON();
 
 					_.each( attachments, function( attachment ) {
-						if ( attachment.sizes.thumbnail ) {
-							attachment.thumbnail = attachment.sizes.thumbnail;
-						} else {
-							attachment.thumbnail = attachment.sizes.full;
+						if ( attachment.sizes ) {
+							if ( attachment.sizes.thumbnail ) {
+								attachment.thumbnail = attachment.sizes.thumbnail;
+							} else if ( attachment.sizes.full ) {
+								attachment.thumbnail = attachment.sizes.full;
+							}
 						}
 					} );
 				}
diff --git a/src/wp-includes/media-template.php b/src/wp-includes/media-template.php
index f73209eac8..92026f2e57 100644
--- a/src/wp-includes/media-template.php
+++ b/src/wp-includes/media-template.php
@@ -975,7 +975,11 @@ function wp_print_media_templates() {
 				<# _.each( data.attachments, function( attachment, index ) { #>
 					<dl class="gallery-item">
 						<dt class="gallery-icon">
-							<img src="{{{ attachment.thumbnail.url }}}" width="{{ attachment.thumbnail.width }}" height="{{ attachment.thumbnail.height }}" />
+							<# if ( attachment.thumbnail ) { #>
+								<img src="{{ attachment.thumbnail.url }}" width="{{ attachment.thumbnail.width }}" height="{{ attachment.thumbnail.height }}" />
+							<# } else { #>
+								<img src="{{ attachment.url }}" />
+							<# } #>
 						</dt>
 						<dd class="wp-caption-text gallery-caption">
 							{{ attachment.caption }}