diff --git a/core/modules/system/css/components/item-list.module.css b/core/modules/system/css/components/item-list.module.css
new file mode 100644
index 0000000..7bddff9
--- /dev/null
+++ b/core/modules/system/css/components/item-list.module.css
@@ -0,0 +1,19 @@
+/**
+ * @file
+ * Styles for item list.
+ */
+
+.item-list__comma-list,
+.item-list__comma-list li {
+  display: inline;
+}
+.item-list__comma-list {
+  margin: 0;
+  padding: 0;
+}
+.item-list__comma-list li:after {
+  content: ", ";
+}
+.item-list__comma-list li:last-child:after {
+  content: "";
+}
diff --git a/core/modules/system/css/components/item-list.theme.css b/core/modules/system/css/components/item-list.theme.css
deleted file mode 100644
index 185e450..0000000
--- a/core/modules/system/css/components/item-list.theme.css
+++ /dev/null
@@ -1,24 +0,0 @@
-/**
- * @file
- * Visual styles for item list.
- */
-ul.item-list__comma-list {
-  display: inline;
-}
-ul.item-list__comma-list li {
-  display: inline;
-  list-style-type: none;
-}
-ul.item-list__comma-list,
-ul.item-list__comma-list li,
-[dir="rtl"] ul.item-list__comma-list,
-[dir="rtl"] ul.item-list__comma-list li {
-  margin: 0;
-  padding: 0;
-}
-ul.item-list__comma-list li:after {
-  content: ", ";
-}
-ul.item-list__comma-list li:last-child:after {
-  content: "";
-}
diff --git a/core/modules/system/system.libraries.yml b/core/modules/system/system.libraries.yml
index 9493f52..8a1a5fd 100644
--- a/core/modules/system/system.libraries.yml
+++ b/core/modules/system/system.libraries.yml
@@ -11,6 +11,7 @@ base:
       css/components/clearfix.module.css: { weight: -10 }
       css/components/details.module.css: { weight: -10 }
       css/components/hidden.module.css: { weight: -10 }
+      css/components/item-list.module.css: { weight: -10 }
       css/components/js.module.css: { weight: -10 }
       css/components/nowrap.module.css: { weight: -10 }
       css/components/position-container.module.css: { weight: -10 }
@@ -31,7 +32,6 @@ base:
       css/components/form.theme.css: { weight: -10 }
       css/components/icons.theme.css: { weight: -10 }
       css/components/inline-form.theme.css: { weight: -10 }
-      css/components/item-list.theme.css: { weight: -10 }
       css/components/link.theme.css: { weight: -10 }
       css/components/links.theme.css: { weight: -10 }
       css/components/menu.theme.css: { weight: -10 }
diff --git a/core/themes/bartik/css/components/item-list.css b/core/themes/bartik/css/components/item-list.css
index eeb4e77..72c6781 100644
--- a/core/themes/bartik/css/components/item-list.css
+++ b/core/themes/bartik/css/components/item-list.css
@@ -10,3 +10,9 @@
 [dir="rtl"] .item-list ul li {
   padding: 0.2em 0 0 0.5em;
 }
+.item-list .item-list__comma-list,
+.item-list .item-list__comma-list li,
+[dir="rtl"] .item-list .item-list__comma-list,
+[dir="rtl"] .item-list .item-list__comma-list li {
+  padding: 0;
+}
diff --git a/core/themes/classy/classy.libraries.yml b/core/themes/classy/classy.libraries.yml
index 8fe5000..6987fce 100644
--- a/core/themes/classy/classy.libraries.yml
+++ b/core/themes/classy/classy.libraries.yml
@@ -1,11 +1,12 @@
 base:
   version: VERSION
   css:
-    theme:
-      css/layout.css: {}
+    component:
       # We can not attach this in the item-list.html.twig template since it is
       # often used during RendererInterface::renderPlain().
-      css/dataset/item-list.css: {}
+      css/components/item-list.css: { weight: -10 }
+    layout:
+      css/layout.css: {}
 
 book-navigation:
   version: VERSION
diff --git a/core/themes/classy/css/components/item-list.css b/core/themes/classy/css/components/item-list.css
new file mode 100644
index 0000000..a538995
--- /dev/null
+++ b/core/themes/classy/css/components/item-list.css
@@ -0,0 +1,32 @@
+/**
+ * @file
+ * Styling for item lists.
+ */
+
+.item-list .title {
+  font-weight: bold;
+}
+.item-list ul {
+  margin: 0 0 0.75em 0;
+  padding: 0;
+}
+.item-list li {
+  margin: 0 0 0.25em 1.5em; /* LTR */
+  padding: 0;
+}
+[dir="rtl"] .item-list li {
+  margin: 0 1.5em 0.25em 0;
+}
+
+/**
+ * Comma separated lists.
+ */
+.item-list--comma-list {
+  display: inline;
+}
+.item-list--comma-list .item-list__comma-list,
+.item-list__comma-list li,
+[dir="rtl"] .item-list--comma-list .item-list__comma-list,
+[dir="rtl"] .item-list__comma-list li {
+  margin: 0;
+}
diff --git a/core/themes/classy/css/dataset/item-list.css b/core/themes/classy/css/dataset/item-list.css
deleted file mode 100644
index da51a40..0000000
--- a/core/themes/classy/css/dataset/item-list.css
+++ /dev/null
@@ -1,38 +0,0 @@
-/**
- * @file
- * Styling for item lists.
- */
-.item-list .title {
-  font-weight: bold;
-}
-.item-list ul {
-  margin: 0 0 0.75em 0;
-  padding: 0;
-}
-.item-list ul li {
-  margin: 0 0 0.25em 1.5em; /* LTR */
-  padding: 0;
-}
-[dir="rtl"] .item-list ul li {
-  margin: 0 1.5em 0.25em 0;
-}
-.item-list--comma-list {
-  display: inline;
-}
-/**
- * Comma separated lists inside lists.
- */
-.item-list ul.item-list__comma-list {
-  display: inline;
-}
-.item-list ul.item-list__comma-list li {
-  display: inline;
-  list-style-type: none;
-}
-.item-list .item-list__comma-list,
-.item-list .item-list__comma-list li,
-[dir="rtl"] .item-list .item-list__comma-list,
-[dir="rtl"] .item-list .item-list__comma-list li {
-  margin: 0;
-  padding: 0;
-}
diff --git a/core/themes/seven/css/components/menus-and-lists.css b/core/themes/seven/css/components/menus-and-lists.css
index 0dc37a6..d96fe55 100644
--- a/core/themes/seven/css/components/menus-and-lists.css
+++ b/core/themes/seven/css/components/menus-and-lists.css
@@ -38,7 +38,3 @@ ul.inline li {
 ul.inline li {
   display: inline;
 }
-.item-list .item-list__comma-list,
-[dir="rtl"] .item-list .item-list__comma-list {
-  margin: 0;
-}