diff --git a/tests/test_litellm/llms/xai/test_xai_chat_transformation.py b/tests/test_litellm/llms/xai/test_xai_chat_transformation.py
index 3fd666e4f50..0a9e3234f12 100644
--- a/tests/test_litellm/llms/xai/test_xai_chat_transformation.py
+++ b/tests/test_litellm/llms/xai/test_xai_chat_transformation.py
@@ -13,6 +13,7 @@ from litellm.types.utils import (
     ModelResponse,
     Usage,
 )
+from litellm.utils import get_optional_params
 
 
 class TestXAIReasoningTokenFolding:
@@ -309,3 +310,15 @@ class TestXAIReportedCost:
             0.0,
             0.0037756,
         )
+
+
+class TestXAIMaxCompletionTokens:
+    def test_max_completion_tokens_is_accepted_and_mapped_to_max_tokens(self):
+        result = get_optional_params(
+            model="grok-4.20-beta",
+            custom_llm_provider="xai",
+            max_completion_tokens=64,
+        )
+
+        assert result["max_tokens"] == 64
+        assert "max_completion_tokens" not in result