diff --git a/core/modules/system/css/components/details.module.css b/core/modules/system/css/components/details.module.css
deleted file mode 100644
index 23ee3b4121d412ac476dd19acd960b20a38323d3..0000000000000000000000000000000000000000
--- a/core/modules/system/css/components/details.module.css
+++ /dev/null
@@ -1,10 +0,0 @@
-/**
- * @file
- * Collapsible details.
- *
- * @see collapse.js
- */
-
-.js details:not([open]) .details-wrapper {
-  display: none;
-}
diff --git a/core/modules/system/system.libraries.yml b/core/modules/system/system.libraries.yml
index 19e3935aa388919a864844c73277aabef558c1c0..a368e7e1f9c87bbb681be1bd8b8e58cc9735dc00 100644
--- a/core/modules/system/system.libraries.yml
+++ b/core/modules/system/system.libraries.yml
@@ -6,7 +6,6 @@ base:
       css/components/align.module.css: { weight: -10 }
       css/components/container-inline.module.css: { weight: -10 }
       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 }
diff --git a/core/themes/stable9/css/system/components/details.module.css b/core/themes/stable9/css/system/components/details.module.css
deleted file mode 100644
index 23ee3b4121d412ac476dd19acd960b20a38323d3..0000000000000000000000000000000000000000
--- a/core/themes/stable9/css/system/components/details.module.css
+++ /dev/null
@@ -1,10 +0,0 @@
-/**
- * @file
- * Collapsible details.
- *
- * @see collapse.js
- */
-
-.js details:not([open]) .details-wrapper {
-  display: none;
-}
diff --git a/core/themes/stable9/stable9.info.yml b/core/themes/stable9/stable9.info.yml
index 70ac743dbd5b4f661a12ab8fc9e77a94ba0050c5..5e276f3634f81cd02ddf8eeb0028221c94746a31 100644
--- a/core/themes/stable9/stable9.info.yml
+++ b/core/themes/stable9/stable9.info.yml
@@ -232,7 +232,6 @@ libraries-override:
         css/components/align.module.css: css/system/components/align.module.css
         css/components/container-inline.module.css: css/system/components/container-inline.module.css
         css/components/clearfix.module.css: css/system/components/clearfix.module.css
-        css/components/details.module.css: css/system/components/details.module.css
         css/components/hidden.module.css: css/system/components/hidden.module.css
         css/components/item-list.module.css: css/system/components/item-list.module.css
         css/components/js.module.css: css/system/components/js.module.css