diff -u b/core/themes/seven/style.css b/core/themes/seven/style.css
--- b/core/themes/seven/style.css
+++ b/core/themes/seven/style.css
@@ -481,6 +481,12 @@
   top: 3px;
   right: 3px; /* LTR */
 }
+/**
+ * Force browsers to calculate the width of a 'select all' TH element.
+ */
+table th.select-all {
+  width: 1px;
+}
 table td.active {
   background: #e9e9dd;
 }
@@ -490,13 +496,6 @@
   top: 3px;
   right: 3px; /* LTR */
 }
-/**
- * Checkbox have different widths size in different browsers. Set width to a minimum
- * value that trigger browsers to automatically size minimum width of TH element.
- */
-table th.select-all {
-  width: 1px;
-}
 table td.active {
   background: #e9e9dd;
 }