diff --git a/core/core.libraries.yml b/core/core.libraries.yml
index 369130c0eb296fe00cf2e1af1e5c85f6215b7043..b90ba9729231e326fe73911a4ea217fc796148b0 100644
--- a/core/core.libraries.yml
+++ b/core/core.libraries.yml
@@ -890,6 +890,7 @@ normalize:
   css:
     base:
       assets/vendor/normalize-css/normalize.css: { weight: -20 }
+      misc/normalize-fixes.css: { weight: -19 }
 
 picturefill:
   remote: https://github.com/scottjehl/picturefill
diff --git a/core/misc/normalize-fixes.css b/core/misc/normalize-fixes.css
new file mode 100644
index 0000000000000000000000000000000000000000..9df0fa0aed4ab774491a2415872c2633f6d7bd45
--- /dev/null
+++ b/core/misc/normalize-fixes.css
@@ -0,0 +1,13 @@
+/**
+ * @file
+ * Fixes for core/assets/vendor/normalize-css/normalize.css since version 3.
+ */
+
+/**
+ * Fix problem with details/summary lines missing the drop arrows.
+ */
+@-moz-document url-prefix() {
+  summary {
+    display: list-item;
+  }
+}