diff -u b/core/tests/Drupal/FunctionalTests/AssertLegacyTrait.php b/core/tests/Drupal/FunctionalTests/AssertLegacyTrait.php
--- b/core/tests/Drupal/FunctionalTests/AssertLegacyTrait.php
+++ b/core/tests/Drupal/FunctionalTests/AssertLegacyTrait.php
@@ -228,14 +228,14 @@
   }
 
   /**
-   * Asserts that a field exists with the given name and value.
+   * Asserts that a field don't exist with the given name and value.
    *
    * @param string $name
    *   Name of field to assert.
    * @param string $value
-   *   (optional) Value of the field to assert. You may pass in NULL (default)
+   *   (optional) Assert field not equal to the Value. You may pass in NULL (default)
    *   to skip checking the actual value, while still checking that the field
-   *   exists.
+   *   don't exist.
    *
    * @deprecated Scheduled for removal in Drupal 9.0.0.
    *   Use $this->assertSession()->fieldNotExists() or
@@ -243,7 +243,7 @@
    */
   protected function assertNoFieldByName($name, $value = '') {
     $this->assertSession()->fieldNotExists($name);
-    if ($value !== NULL) {
+    if ($value !== '') {
       $this->assertSession()->fieldValueNotEquals($name, (string) $value);
     }
   }