diff --git a/core/modules/taxonomy/taxonomy.test b/core/modules/taxonomy/taxonomy.test
index a7f7bd9..a3a5fe0 100644
--- a/core/modules/taxonomy/taxonomy.test
+++ b/core/modules/taxonomy/taxonomy.test
@@ -648,6 +648,10 @@ class TaxonomyTermTestCase extends TaxonomyWebTestCase {
     $input = substr($term_objects['term3']->name, 0, 3);
     $this->drupalGet('taxonomy/autocomplete/taxonomy_' . $this->vocabulary->machine_name . '/' . $input);
     $this->assertRaw('{"' . $term_objects['term3']->name . '":"' . $term_objects['term3']->name . '"}', t('Autocomplete returns term %term_name after typing the first 3 letters.', array('%term_name' => $term_objects['term3']->name)));
+
+    // Test the autocomplete path without passing a field_name and terms.
+    // This should not trigger a PHP notice.
+    $this->drupalGet('taxonomy/autocomplete');
   }
 
   /**