diff --git a/app/models/custom_workflow.rb b/app/models/custom_workflow.rb
index 6f8e483..63f6746 100644
--- a/app/models/custom_workflow.rb
+++ b/app/models/custom_workflow.rb
@@ -134,7 +134,7 @@ def validate_syntax_for(object, event)
     object.instance_eval(self[event]) if respond_to?(event) && self[event]
   rescue RedmineCustomWorkflows::Errors::WorkflowError => _e
     # Do nothing
-  rescue StandardError => e
+  rescue StandardError, ScriptError => e
     errors.add event, :invalid_script, error: e
   end
 
diff --git a/app/models/custom_workflow_mailer.rb b/app/models/custom_workflow_mailer.rb
index 5c81da3..dcc555b 100644
--- a/app/models/custom_workflow_mailer.rb
+++ b/app/models/custom_workflow_mailer.rb
@@ -37,8 +37,8 @@ def custom_email(user, headers)
     template_params = headers.delete(:template_params) || {}
     if text_body || html_body
       mail headers do |format|
-        format.text { render text: text_body } if text_body
-        format.html { render text: html_body } if html_body
+        format.text { render plain: text_body } if text_body.present?
+        format.html { render plain: html_body } if html_body.present? && !Setting.plain_text_mail?
       end
     elsif template_name
       template_params.each { |k, v| instance_variable_set("@#{k}", v) }
diff --git a/test/unit/custom_workflow_mailer_test.rb b/test/unit/custom_workflow_mailer_test.rb
index ed5ba90..027d780 100644
--- a/test/unit/custom_workflow_mailer_test.rb
+++ b/test/unit/custom_workflow_mailer_test.rb
@@ -42,8 +42,22 @@ def test_truth
   def test_custom_email
     CustomWorkflowMailer.deliver_custom_email @user2, subject: 'Subject', text_body: 'Body', html_body: 'Body'
     email = last_email
-    assert text_part(email).body.include? 'Body'
-    assert html_part(email).body.include? 'Body'
+    text = text_part(email).body
+    html = html_part(email).body
+    assert text.include?('Body'), "'Body' expected\n'#{text}' present'"
+    assert html.include?('Body'), "'Body' expected\n'#{html}' present'"
+  end
+
+  def test_custom_email_template
+    CustomWorkflowMailer.deliver_custom_email @user2,
+                                              subject: 'Subject',
+                                              template_name: 'mailer/test_email',
+                                              template_params: { url: Setting.host_name }
+    email = last_email
+    text = text_part(email).body
+    html = html_part(email).body
+    assert text.include?(Setting.host_name), "'#{Setting.host_name} expected\n'#{text}' present'"
+    assert html.include?(Setting.host_name), "'#{Setting.host_name} expected\n'#{html}' present'"
   end
 
   private