diff --git a/src/wp-includes/customize/class-wp-customize-site-icon-control.php b/src/wp-includes/customize/class-wp-customize-site-icon-control.php
index 58fea53757..5f18563b14 100644
--- a/src/wp-includes/customize/class-wp-customize-site-icon-control.php
+++ b/src/wp-includes/customize/class-wp-customize-site-icon-control.php
@@ -67,11 +67,11 @@ class WP_Customize_Site_Icon_Control extends WP_Customize_Cropped_Image_Control
 							<img src="<?php echo esc_url( admin_url( 'images/' . ( is_rtl() ? 'browser-rtl.png' : 'browser.png' ) ) ); ?>" class="browser-preview" width="182" alt="" />
 
 							<div class="favicon">
-								<img src="{{ data.attachment.sizes.full.url }}" alt="<?php esc_attr_e( 'Preview as a browser icon' ); ?>"/>
+								<img src="{{ data.attachment.sizes.full ? data.attachment.sizes.full.url : data.attachment.url }}" alt="<?php esc_attr_e( 'Preview as a browser icon' ); ?>"/>
 							</div>
 							<span class="browser-title" aria-hidden="true"><?php bloginfo( 'name' ); ?></span>
 						</div>
-						<img class="app-icon-preview" src="{{ data.attachment.sizes.full.url }}" alt="<?php esc_attr_e( 'Preview as an app icon' ); ?>"/>
+						<img class="app-icon-preview" src="{{ data.attachment.sizes.full ? data.attachment.sizes.full.url : data.attachment.url }}" alt="<?php esc_attr_e( 'Preview as an app icon' ); ?>"/>
 					</div>
 				<# } #>
 				<div class="actions">