diff --git a/core/modules/config/src/Form/ConfigImportForm.php b/core/modules/config/src/Form/ConfigImportForm.php
index c16dfe8..733e1d1 100644
--- a/core/modules/config/src/Form/ConfigImportForm.php
+++ b/core/modules/config/src/Form/ConfigImportForm.php
@@ -72,6 +72,11 @@ public function buildForm(array $form, FormStateInterface $form_state) {
    * {@inheritdoc}
    */
   public function validateForm(array &$form, FormStateInterface $form_state) {
+    $directory = config_get_config_directory(CONFIG_SYNC_DIRECTORY);
+    if (!is_writable($directory)) {
+      $form_state->setErrorByName('import_tarball', $this->t('The directory %directory is not writable.', ['%directory' => $directory]));
+    }
+
     $file_upload = $this->getRequest()->files->get('files[import_tarball]', NULL, TRUE);
     if ($file_upload && $file_upload->isValid()) {
       $form_state->setValue('import_tarball', $file_upload->getRealPath());
diff --git a/core/modules/config/src/Tests/ConfigImportUploadTest.php b/core/modules/config/src/Tests/ConfigImportUploadTest.php
index 33f6171..da1e159 100644
--- a/core/modules/config/src/Tests/ConfigImportUploadTest.php
+++ b/core/modules/config/src/Tests/ConfigImportUploadTest.php
@@ -50,6 +50,12 @@ function testImport() {
     $edit = array('files[import_tarball]' => drupal_realpath($text_file->uri));
     $this->drupalPostForm('admin/config/development/configuration/full/import', $edit, t('Upload'));
     $this->assertText(t('Could not extract the contents of the tar file'));
+
+    // Make the sync directory read-only.
+    $directory = config_get_config_directory(CONFIG_SYNC_DIRECTORY);
+    \Drupal::service('file_system')->chmod($directory, 0555);
+    $this->drupalPostForm('admin/config/development/configuration/full/import', $edit, t('Upload'));
+    $this->assertRaw(t('The directory %directory is not writable.', ['%directory' => $directory]));
   }
 
 }