diff --git a/lib/ai_helper/assistant.rb b/lib/ai_helper/assistant.rb
index 99af0d3d..aa360a7e 100644
--- a/lib/ai_helper/assistant.rb
+++ b/lib/ai_helper/assistant.rb
@@ -29,7 +29,9 @@ module DiscourseAi
               prompts.map do |prompt|
                 if prompt.name == "translate"
                   locale = user.effective_locale
-                  locale_hash = LocaleSiteSetting.language_names[locale]
+                  locale_hash =
+                    LocaleSiteSetting.language_names[locale] ||
+                      LocaleSiteSetting.language_names[locale.split("_")[0]]
                   translation =
                     I18n.t(
                       "discourse_ai.ai_helper.prompts.translate",
diff --git a/spec/lib/modules/ai_helper/assistant_spec.rb b/spec/lib/modules/ai_helper/assistant_spec.rb
index fd3f479c..83233116 100644
--- a/spec/lib/modules/ai_helper/assistant_spec.rb
+++ b/spec/lib/modules/ai_helper/assistant_spec.rb
@@ -59,6 +59,11 @@ RSpec.describe DiscourseAi::AiHelper::Assistant do
       )
     end
 
+    it "does not raise an error when effective_locale does not exactly match keys in LocaleSiteSetting" do
+      SiteSetting.default_locale = "zh_CN"
+      expect { subject.available_prompts(user) }.not_to raise_error
+    end
+
     context "when illustrate post model is enabled" do
       before do
         SiteSetting.ai_helper_illustrate_post_model = "stable_diffusion_xl"