diff --git a/aider/coders/base_coder.py b/aider/coders/base_coder.py
index 4c7324ac7..c478db43b 100755
--- a/aider/coders/base_coder.py
+++ b/aider/coders/base_coder.py
@@ -1082,7 +1082,8 @@ class Coder:
             "ko": "Korean",
             "ru": "Russian",
         }
-        return fallback.get(lang_code.split("_")[0].lower(), lang_code)
+        primary_lang_code = lang_code.replace("-", "_").split("_")[0].lower()
+        return fallback.get(primary_lang_code, lang_code)
 
     def get_user_language(self):
         """
diff --git a/tests/basic/test_coder.py b/tests/basic/test_coder.py
index 2f250d858..bb93ad107 100644
--- a/tests/basic/test_coder.py
+++ b/tests/basic/test_coder.py
@@ -1202,6 +1202,7 @@ This command will print 'Hello, World!' to the console."""
             self.assertEqual(coder.normalize_language("fr_FR"), "French")
             self.assertEqual(coder.normalize_language("es"), "Spanish")
             self.assertEqual(coder.normalize_language("de_DE.UTF-8"), "German")
+            self.assertEqual(coder.normalize_language("zh-CN"), "Chinese") # Test hyphen in fallback
             self.assertEqual(coder.normalize_language("ja"), "Japanese")
             self.assertEqual(
                 coder.normalize_language("unknown_code"), "unknown_code"