diff --git a/core/themes/seven/css/components/system-status-report.css b/core/themes/seven/css/components/system-status-report.css
index 9e4a9c7..498ad52 100644
--- a/core/themes/seven/css/components/system-status-report.css
+++ b/core/themes/seven/css/components/system-status-report.css
@@ -165,6 +165,8 @@ html:not(.details) .system-status-report__status-title {
 [dir="rtl"] .system-status-report__status-title::-webkit-details-marker {
   float: left;
 }
+
+/* Make poly-filled details and summary elements behave correctly. */
 .system-status-report summary:first-child ~ * {
   display: none;
 }
@@ -172,6 +174,7 @@ html:not(.details) .system-status-report__status-title {
 .system-status-report details > summary:first-child {
   display: block;
 }
+
 .system-status-report__status-title .details-title:before,
 .details .system-status-report__status-icon:before {
   content: "";
@@ -224,7 +227,7 @@ html:not(.details) .system-status-report__status-title {
     clear: both;
   }
   .system-status-report details > summary:first-child {
-    width: 35ch;
+    width: 18rem;
     float: left; /* LTR */
   }
   [dir="rtl"] .system-status-report details > summary:first-child {