diff -u b/core/assets/vendor/normalize-css/normalize-fixes.css b/core/assets/vendor/normalize-css/normalize-fixes.css
--- b/core/assets/vendor/normalize-css/normalize-fixes.css
+++ b/core/assets/vendor/normalize-css/normalize-fixes.css
@@ -8,4 +8,6 @@
  */
-summary {
-  display: list-item;
+@-moz-document url-prefix() {
+  summary {
+    display: list-item;
+  }
 }
diff -u b/core/core.libraries.yml b/core/core.libraries.yml
--- b/core/core.libraries.yml
+++ b/core/core.libraries.yml
@@ -890,7 +890,7 @@
   css:
     base:
       assets/vendor/normalize-css/normalize.css: { weight: -20 }
-      assets/vendor/normalize-css/normalize-fixes.css: { weight: -19, browsers: { IE: false } }
+      assets/vendor/normalize-css/normalize-fixes.css: { weight: -19 }
 
 picturefill:
   remote: https://github.com/scottjehl/picturefill