diff -u b/core/includes/theme.inc b/core/includes/theme.inc
--- b/core/includes/theme.inc
+++ b/core/includes/theme.inc
@@ -1066,7 +1066,6 @@
   }
 }
 
-
 /**
  * Prepares variables for inline list templates.
  *
@@ -1075,15 +1074,17 @@
  * @param array $variables
  *   An associative array containing:
  *   - items: An array of items to be displayed in the list.
+ *   - separator: A string to separate list items.
+ *   - empty: A message to display when there are no items.
  *
  * @see https://www.drupal.org/node/1842756
  */
 function template_preprocess_inline_list(&$variables) {
-  // Since the separator may be user-specified, it must be sanitized.
+  // Since the separator may be user-specified, it must be filtered to permit
+  // some HTML (such as <br />) to pass through.
   $variables['separator'] = SafeString::create(Xss::filterAdmin($variables['separator']));
 }
 
-
 /**
  * Returns HTML for an indentation div; used for drag and drop tables.
  *
diff -u b/core/modules/system/src/Tests/Theme/FunctionsTest.php b/core/modules/system/src/Tests/Theme/FunctionsTest.php
--- b/core/modules/system/src/Tests/Theme/FunctionsTest.php
+++ b/core/modules/system/src/Tests/Theme/FunctionsTest.php
@@ -185,8 +185,8 @@
     // Verify that empty text is not displayed when there are list items.
     $variables = array();
     $variables['empty'] = 'No items found.';
-    $variables['items'] = array('Un', 'Deux', 'Trois');
-    $expected = 'Un, Deux, Trois';
+    $variables['items'] = array('Rabbit', 'rabbit', 'rabbit');
+    $expected = 'Rabbit, rabbit, rabbit';
     $this->assertThemeOutput('inline_list', $variables, $expected, '%callback does not print empty text when there are list items.');
 
     // Verify that a non-default separator is rendered
@@ -198,9 +198,9 @@
 
     // Verify that HTML separators are properly rendered
     $variables = array();
-    $variables['items'] = array('Un', 'Deux', 'Trois');
+    $variables['items'] = array('Doe', 'Buck', 'Kit');
     $variables['separator'] = '<br />';
-    $expected = 'Un<br />Deux<br />Trois';
+    $expected = 'Doe<br />Buck<br />Kit';
     $this->assertThemeOutput('inline_list', $variables, $expected, '%callback allows HTML in user-provided separators.');
 
     // Verify that the separator is sanitized