diff --git a/core/themes/classy/classy.libraries.yml b/core/themes/classy/classy.libraries.yml
index eb5e0b2..31af031 100644
--- a/core/themes/classy/classy.libraries.yml
+++ b/core/themes/classy/classy.libraries.yml
@@ -91,3 +91,9 @@ user:
   css:
     component:
       css/components/user.css: { weight: -10 }
+
+image-widget:
+  version: VERSION
+  css:
+    component:
+      css/components/image-widget.css: {}
diff --git a/core/themes/classy/css/components/image-widget.css b/core/themes/classy/css/components/image-widget.css
index 3da51ef..b14ecad 100644
--- a/core/themes/classy/css/components/image-widget.css
+++ b/core/themes/classy/css/components/image-widget.css
@@ -1,6 +1,16 @@
-
 /**
+ * @file
  * Image upload widget.
+ *
+ * This CSS file is not used in this theme (Classy). It was intended to be used,
+ * but due to a bug, Drupal 8 shipped with it not being used. To not break
+ * backwards compatibility, we continue to not load it in Classy. Every
+ * subtheme of Classy is encouraged to use it, by attaching the
+ * classy/image-widget asset library in their image-widget.html.twig file.
+ *
+ * @see core/themes/seven/templates/content-edit/image-widget.html.twig.
+ *
+ * @todo In Drupal 9, let core/themes/classy/templates/content-edit/image-widget.html.twig attach the classy/image-widget asset library.
  */
 .image-preview {
   float: left; /* LTR */
diff --git a/core/themes/classy/templates/content-edit/image-widget.html.twig b/core/themes/classy/templates/content-edit/image-widget.html.twig
index 5e8033f..dac3a22 100644
--- a/core/themes/classy/templates/content-edit/image-widget.html.twig
+++ b/core/themes/classy/templates/content-edit/image-widget.html.twig
@@ -10,7 +10,6 @@
  * @see template_preprocess_image_widget()
  */
 #}
-{{ attach_library('classy/image-widget') }}
 <div{{ attributes }}>
   {% if data.preview %}
     <div class="image-preview">
diff --git a/core/themes/seven/templates/image-widget.html.twig b/core/themes/seven/templates/image-widget.html.twig
new file mode 100644
index 0000000..0544e4d
--- /dev/null
+++ b/core/themes/seven/templates/image-widget.html.twig
@@ -0,0 +1,12 @@
+{#
+/**
+ * @file
+ * Theme override for an image field widget.
+ *
+ * Include from Classy theme.
+ *
+ * @see template_preprocess_image_widget()
+ */
+#}
+{% include '@classy/content-edit/image-widget.html.twig' %}
+{{ attach_library('classy/image-widget') }}