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
@@ -42,6 +42,19 @@
     $expected = '';
     $this->assertThemeOutput('item_list', $variables, $expected, 'Empty %callback with title generates no output.');
 
+    // Verify that empty items produce the empty string.
+    $variables = array();
+    $variables['empty'] = 'No items found.';
+    $expected = '<div class="item-list">No items found.</div>';
+    $this->assertThemeOutput('item_list', $variables, $expected, 'Empty %callback generates empty string.');
+
+    // Verify that empty items produce the empty string with title.
+    $variables = array();
+    $variables['title'] = 'Some title';
+    $variables['empty'] = 'No items found.';
+    $expected = '<div class="item-list"><h3>Some title</h3>No items found.</div>';
+    $this->assertThemeOutput('item_list', $variables, $expected, 'Empty %callback generates empty string with title.');
+
     // Verify that title set to 0 is output.
     $variables = array();
     $variables['title'] = 0;