diff --git a/core/modules/comment/src/Plugin/migrate/source/d6/CommentVariable.php b/core/modules/comment/src/Plugin/migrate/source/d6/CommentVariable.php
index 4417e912b1354d4fd40a671748fbd4658a3e320f..7b92da9961a95f8a22b58f9937b3cc38d97a19d4 100644
--- a/core/modules/comment/src/Plugin/migrate/source/d6/CommentVariable.php
+++ b/core/modules/comment/src/Plugin/migrate/source/d6/CommentVariable.php
@@ -30,7 +30,7 @@ protected function initializeIterator() {
   /**
    * {@inheritdoc}
    */
-  public function count() {
+  public function count($refresh = FALSE) {
     return count($this->getCommentVariables());
   }
 
diff --git a/core/modules/field/src/Plugin/migrate/source/d7/FieldInstance.php b/core/modules/field/src/Plugin/migrate/source/d7/FieldInstance.php
index a54b17d9d162b0ca8a3551d83ec2e3e682203a52..452c6bbfde480c4d795a1eefed808075f2a7685e 100644
--- a/core/modules/field/src/Plugin/migrate/source/d7/FieldInstance.php
+++ b/core/modules/field/src/Plugin/migrate/source/d7/FieldInstance.php
@@ -145,7 +145,7 @@ public function getIds() {
   /**
    * {@inheritdoc}
    */
-  public function count() {
+  public function count($refresh = FALSE) {
     return $this->initializeIterator()->count();
   }
 
diff --git a/core/modules/file/src/Plugin/migrate/source/d6/UploadInstance.php b/core/modules/file/src/Plugin/migrate/source/d6/UploadInstance.php
index 17c34bf3abd00dfc58853fd8b02b1094b78a285b..f4182a927e19b7ec6a4027b53c46a8d0b6da9795 100644
--- a/core/modules/file/src/Plugin/migrate/source/d6/UploadInstance.php
+++ b/core/modules/file/src/Plugin/migrate/source/d6/UploadInstance.php
@@ -78,7 +78,7 @@ public function fields() {
   /**
    * {@inheritdoc}
    */
-  public function count() {
+  public function count($refresh = FALSE) {
     return count($this->initializeIterator());
   }
 
diff --git a/core/modules/migrate/src/Plugin/migrate/source/DummyQueryTrait.php b/core/modules/migrate/src/Plugin/migrate/source/DummyQueryTrait.php
index b77f95e2736712d9f72fb48cd0afe6677612d619..efe56b41fa2629869a40bb6c79decf833608c7d6 100644
--- a/core/modules/migrate/src/Plugin/migrate/source/DummyQueryTrait.php
+++ b/core/modules/migrate/src/Plugin/migrate/source/DummyQueryTrait.php
@@ -27,7 +27,7 @@ public function query() {
   /**
    * {@inheritdoc}
    */
-  public function count() {
+  public function count($refresh = FALSE) {
     return 1;
   }
 
diff --git a/core/modules/migrate/src/Plugin/migrate/source/SourcePluginBase.php b/core/modules/migrate/src/Plugin/migrate/source/SourcePluginBase.php
index 429a1457a814caf3c20818de15d2e5270930f585..94e5c221a90ce344dd858a66c35504d243fe09c9 100644
--- a/core/modules/migrate/src/Plugin/migrate/source/SourcePluginBase.php
+++ b/core/modules/migrate/src/Plugin/migrate/source/SourcePluginBase.php
@@ -436,7 +436,10 @@ public function getCurrentIds() {
    * Returns -1 if the source is not countable.
    *
    * @param bool $refresh
-   *   (optional) Whether or not to refresh the count. Defaults to FALSE.
+   *   (optional) Whether or not to refresh the count. Defaults to FALSE. Not
+   *   all implementations support the reset flag. In such instances this
+   *   parameter is ignored and the result of calling the method will always be
+   *   up to date.
    *
    * @return int
    *   The count.
diff --git a/core/modules/migrate/src/Plugin/migrate/source/SqlBase.php b/core/modules/migrate/src/Plugin/migrate/source/SqlBase.php
index 881e2fbcf62cd632373ebbe5beb6a3f3b4ef02ba..35ab8abd859e5de3f99771375c43a49210d95c7a 100644
--- a/core/modules/migrate/src/Plugin/migrate/source/SqlBase.php
+++ b/core/modules/migrate/src/Plugin/migrate/source/SqlBase.php
@@ -365,7 +365,7 @@ abstract public function query();
   /**
    * {@inheritdoc}
    */
-  public function count() {
+  public function count($refresh = FALSE) {
     return $this->query()->countQuery()->execute()->fetchField();
   }
 
diff --git a/core/modules/migrate_drupal/src/Plugin/migrate/source/Variable.php b/core/modules/migrate_drupal/src/Plugin/migrate/source/Variable.php
index 410acec229cff80481fe94f4a5236794c1ace785..e127dfbdc87a84da0b589217be43545f2e61ad4a 100644
--- a/core/modules/migrate_drupal/src/Plugin/migrate/source/Variable.php
+++ b/core/modules/migrate_drupal/src/Plugin/migrate/source/Variable.php
@@ -58,7 +58,7 @@ protected function values() {
   /**
    * {@inheritdoc}
    */
-  public function count() {
+  public function count($refresh = FALSE) {
     return intval($this->query()->countQuery()->execute()->fetchField() > 0);
   }
 
diff --git a/core/modules/migrate_drupal/src/Plugin/migrate/source/d6/VariableTranslation.php b/core/modules/migrate_drupal/src/Plugin/migrate/source/d6/VariableTranslation.php
index 566a8402e0d44179716234b9e2e7b9d0c5035682..f2ca8b73aa541d202950d714a6b4e691a0a07590 100644
--- a/core/modules/migrate_drupal/src/Plugin/migrate/source/d6/VariableTranslation.php
+++ b/core/modules/migrate_drupal/src/Plugin/migrate/source/d6/VariableTranslation.php
@@ -68,7 +68,7 @@ protected function values() {
   /**
    * {@inheritdoc}
    */
-  public function count() {
+  public function count($refresh = FALSE) {
     return $this->initializeIterator()->count();
   }
 
diff --git a/core/modules/node/src/Plugin/migrate/source/d6/ViewModeBase.php b/core/modules/node/src/Plugin/migrate/source/d6/ViewModeBase.php
index 315f069a6196d637951369e7e4130b80e3cfcaac..88d84d95249fd1c2fc9068788730aaaff48589ea 100644
--- a/core/modules/node/src/Plugin/migrate/source/d6/ViewModeBase.php
+++ b/core/modules/node/src/Plugin/migrate/source/d6/ViewModeBase.php
@@ -12,7 +12,7 @@ abstract class ViewModeBase extends DrupalSqlBase {
   /**
    * {@inheritdoc}
    */
-  public function count() {
+  public function count($refresh = FALSE) {
     return count($this->initializeIterator());
   }