diff --git a/core/modules/workflows/src/Form/WorkflowStateAddForm.php b/core/modules/workflows/src/Form/WorkflowStateAddForm.php
index b15c75720f..3011fef97b 100644
--- a/core/modules/workflows/src/Form/WorkflowStateAddForm.php
+++ b/core/modules/workflows/src/Form/WorkflowStateAddForm.php
@@ -87,14 +87,12 @@ protected function copyFormValuesToEntity(EntityInterface $entity, array $form,
     $values = $form_state->getValues();
 
     try {
-      // Replicate the validation that Workflow::addState() does internally as the
-      // form values have not been validated at this point.
       if (!$entity->hasState($values['id'])) {
         $entity->addState($values['id'], $values['label']);
         if (isset($values['type_settings'])) {
           $configuration = $entity->getTypePlugin()->getConfiguration();
-          $configuration['states'][$values['id']] = $values['type_settings'][$entity->getTypePlugin()
-                ->getPluginId()];
+          // @todo move to submitStateConfigurationForm. #2849827.
+          $configuration['states'][$values['id']] += $values['type_settings'][$entity->getTypePlugin()->getPluginId()];
           $entity->set('type_settings', $configuration);
         }
       }
diff --git a/core/modules/workflows/src/Form/WorkflowTransitionAddForm.php b/core/modules/workflows/src/Form/WorkflowTransitionAddForm.php
index bc9d3908c8..9b569ba33f 100644
--- a/core/modules/workflows/src/Form/WorkflowTransitionAddForm.php
+++ b/core/modules/workflows/src/Form/WorkflowTransitionAddForm.php
@@ -113,8 +113,7 @@ protected function copyFormValuesToEntity(EntityInterface $entity, array $form,
       $entity->addTransition($values['id'], $values['label'], array_filter($values['from']), $values['to']);
       if (isset($values['type_settings'])) {
         $configuration = $entity->getTypePlugin()->getConfiguration();
-        $configuration['transitions'][$values['id']] = $values['type_settings'][$entity->getTypePlugin()
-          ->getPluginId()];
+        $configuration['transitions'][$values['id']] += $values['type_settings'][$entity->getTypePlugin()->getPluginId()];
         $entity->set('type_settings', $configuration);
       }
     }
diff --git a/core/modules/workflows/src/Plugin/WorkflowTypeBase.php b/core/modules/workflows/src/Plugin/WorkflowTypeBase.php
index 1c0724ade3..8fdadeedfa 100644
--- a/core/modules/workflows/src/Plugin/WorkflowTypeBase.php
+++ b/core/modules/workflows/src/Plugin/WorkflowTypeBase.php
@@ -164,7 +164,7 @@ public function addState($state_id, $label) {
       throw new \InvalidArgumentException("The state '$state_id' already exists in workflow.");
     }
     if (preg_match(static::VALID_ID_REGEX, $state_id)) {
-      throw new \InvalidArgumentException("The state ID '$state_id' must contain only lowercase letters, numbers, and underscores");
+      throw new \InvalidArgumentException("The state ID '$state_id' must contain only lowercase letters, numbers, and underscores, but not solely numbers.");
     }
     $this->configuration['states'][$state_id] = [
       'label' => $label,
@@ -267,7 +267,7 @@ public function addTransition($transition_id, $label, array $from_state_ids, $to
       throw new \InvalidArgumentException("The transition '$transition_id' already exists in workflow.'");
     }
     if (preg_match(static::VALID_ID_REGEX, $transition_id)) {
-      throw new \InvalidArgumentException("The transition ID '$transition_id' must contain only lowercase letters, numbers, and underscores.");
+      throw new \InvalidArgumentException("The transition ID '$transition_id' must contain only lowercase letters, numbers, and underscores, but not solely numbers.");
     }
 
     if (!$this->hasState($to_state_id)) {