diff -u b/core/modules/config_translation/src/Form/ConfigTranslationFormBase.php b/core/modules/config_translation/src/Form/ConfigTranslationFormBase.php
--- b/core/modules/config_translation/src/Form/ConfigTranslationFormBase.php
+++ b/core/modules/config_translation/src/Form/ConfigTranslationFormBase.php
@@ -199,13 +199,28 @@
     $form_values = $form_state->getValue(array('translation', 'config_names'));
     foreach ($this->mapper->getConfigNames() as $name) {
       foreach ($form_values[$name] as $key => $value) {
-        // Check that the submitted config value is safe.
-        if (is_string($value) && !locale_string_is_safe($value)) {
+        // Assume submitted value is safe unless otherwise determined.
+        $is_safe = TRUE;
+        // Is the submitted value an array?
+        if (is_array($value)) {
+          // Walk through the array to check each value.
+          array_walk_recursive($value, function(&$item) use (&$is_safe) {
+            // If is a string and not safe.
+            if (is_string($item) && !locale_string_is_safe($item)) {
+              $is_safe = FALSE;
+            }
+          });
+        }
+        // If is a string value, check if it is not safe.
+        elseif (is_string($value) && !locale_string_is_safe($value)) {
+          $is_safe = FALSE;
+        }
+        // Is the submitted value deemed not safe?
+        if (!$is_safe) {
           // Retrieve field label and name attribute.
-          $label = $form['config_names'][$name][$key]['translation']['#title'];
-          $field_name = $form['config_names'][$name][$key]['translation']['#name'];
+          $field_name = 'translation[config_names][' . $name . '][' . $key;
           // Field value is not safe, display error.
-          $form_state->setErrorByName($field_name, $this->t('The submitted %label value contains disallowed HTML', array('%label' => $label)));
+          $form_state->setErrorByName($field_name, $this->t('The submitted string contains disallowed HTML.'));
         }
       }
     }