diff --git a/core/modules/rest/tests/src/Functional/EntityResource/EntityResourceTestBase.php b/core/modules/rest/tests/src/Functional/EntityResource/EntityResourceTestBase.php
index 03ae3a0..6039d2c 100644
--- a/core/modules/rest/tests/src/Functional/EntityResource/EntityResourceTestBase.php
+++ b/core/modules/rest/tests/src/Functional/EntityResource/EntityResourceTestBase.php
@@ -285,6 +285,23 @@ protected function getNormalizedPatchEntity() {
   }
 
   /**
+   * Gets the second normalized POST entity.
+   *
+   * Entity types can have non-sequential IDs, and in that case the second
+   * entity created for POST testing needs to be able to specify a different ID.
+   *
+   * @see ::testPost
+   * @see ::getNormalizedPostEntity
+   *
+   * @return array
+   *   An array structure as returned by ::getNormalizedPostEntity().
+   */
+  protected function getSecondNormalizedPostEntity() {
+    // Return the values of the "parent" method by default.
+    return $this->getNormalizedPostEntity();
+  }
+
+  /**
    * Gets the normalized POST entity with random values for its unique fields.
    *
    * @see ::testPost