diff --git a/core/lib/Drupal/Core/Entity/Sql/SqlContentEntityStorageSchema.php b/core/lib/Drupal/Core/Entity/Sql/SqlContentEntityStorageSchema.php
index ecfa56409a..29c6aebb41 100644
--- a/core/lib/Drupal/Core/Entity/Sql/SqlContentEntityStorageSchema.php
+++ b/core/lib/Drupal/Core/Entity/Sql/SqlContentEntityStorageSchema.php
@@ -1370,13 +1370,8 @@ protected function createSharedTableSchema(FieldStorageDefinitionInterface $stor
                 $new_keys = ['primary key' => $schema[$table_name]['primary key']];
 
                 // If the field is part of a primary key, it might be a serial
-                // field. Serial fields are incorrectly stored as integer fields
-                // in the field schema, so we adapt the schema here manually.
-                // @todo Remove this in
-                //  https://www.drupal.org/project/drupal/issues/2928906
-                $base_table_serial = ($created_field_name === $this->entityType->getKey('id')) && ($table_name === $this->storage->getBaseTable());
-                $revision_table_serial = ($created_field_name === $this->entityType->getKey('revision')) && ($table_name === $this->storage->getRevisionTable());
-                if (($specifier['type'] === 'int') && ($base_table_serial || $revision_table_serial)) {
+                // field.
+                if (($specifier['type'] === 'int') && $this->isSerialField($schema[$table_name], $table_name, $created_field_name)) {
                   $specifier['type'] = 'serial';
                 }
               }
@@ -1682,6 +1677,21 @@ protected function updateSharedTableSchema(FieldStorageDefinitionInterface $stor
               // Check if the field is part of the primary keys.
               if (isset($entity_schema[$table_name]['primary key']) && array_intersect($column_names, $entity_schema[$table_name]['primary key'])) {
                 $schema_handler->addPrimaryKey($table_name, $entity_schema[$table_name]['primary key']);
+
+                // If the field being updated is a serial field, it will have
+                // been changed to an integer field by
+                // SqlContentEntityStorageSchema::dropPrimaryKey() above.
+                // Convert it back now that the primary key has been recreated.
+                if ($this->isSerialField($schema[$table_name], $table_name, $updated_field_name)) {
+                  foreach ($schema[$table_name]['primary key'] as $column_name) {
+                    $spec = $schema[$table_name]['fields'][$column_name];
+                    if ($spec['type'] === 'int') {
+                      $spec['type'] = 'serial';
+                      $schema_handler->changeField($table_name, $column_name, $column_name, $spec);
+                    }
+                  }
+                }
+
                 break;
               }
             }
@@ -2439,13 +2449,7 @@ private function dropPrimaryKey(FieldStorageDefinitionInterface $storage_definit
       // Dropping a primary key must not leave a serial key, so we need to
       // change any serial field to integer first.
       $field_name = $storage_definition->getName();
-      // Serial fields are incorrectly stored as integer fields in the field
-      // schema, so we explicitly check the conditions for marking it serial.
-      // @todo Remove this in
-      //  https://www.drupal.org/project/drupal/issues/2928906
-      $base_table_serial = ($field_name === $this->entityType->getKey('id')) && ($table_name === $this->storage->getBaseTable());
-      $revision_table_serial = ($field_name === $this->entityType->getKey('revision')) && ($table_name === $this->storage->getRevisionTable());
-      if ($base_table_serial || $revision_table_serial) {
+      if ($this->isSerialField($schema, $table_name, $field_name)) {
         foreach ($schema['primary key'] as $column_name) {
           if ($schema['fields'][$column_name]['type'] === 'int') {
             $schema_handler->changeField($table_name, $column_name, $column_name, $schema['fields'][$column_name]);
@@ -2456,4 +2460,38 @@ private function dropPrimaryKey(FieldStorageDefinitionInterface $storage_definit
     }
   }
 
+  /**
+   * Checks whether the a field is a serial field in a given table.
+   *
+   * Because the field schema is incorrectly stored as 'int' we have to manually
+   * call SqlContentEntityStorageSchema::processIdentifierSchema() assuming the
+   * conditions are correct.
+   *
+   * @param array $schema
+   *   The table schema.
+   * @param $table_name
+   *   The table name.
+   * @param $field_name
+   *   The field name.
+   *
+   * @return bool
+   *   TRUE if the field is a serial field in the given table; FALSE otherwise.
+   *
+   * @internal
+   *
+   * @todo Remove this in https://www.drupal.org/project/drupal/issues/2928906
+   */
+  private function isSerialField(array $schema, $table_name, $field_name) {
+    // The ID field is serial in the base table.
+    $is_base_table = ($table_name === $this->storage->getBaseTable());
+    $is_revision_table = ($table_name === $this->storage->getRevisionTable());
+    $is_id = ($field_name === $this->entityType->getKey('id'));
+    $is_revision_id = ($field_name === $this->entityType->getKey('revision'));
+    if (($is_base_table && $is_id) || ($is_revision_table && $is_revision_id)) {
+      $this->processIdentifierSchema($schema, $field_name);
+      return $schema['fields'][$field_name]['type'] === 'serial';
+    }
+    return FALSE;
+  }
+
 }