diff --git a/litellm/litellm_core_utils/tool_fields.py b/litellm/litellm_core_utils/tool_fields.py
index 7467b0b4f8d..3519c13fd9f 100644
--- a/litellm/litellm_core_utils/tool_fields.py
+++ b/litellm/litellm_core_utils/tool_fields.py
@@ -222,6 +222,7 @@ def tool_params_without_hosted_mcp(params: _ParamsT, model: str, route: str, dro
     if kept_tools:
         kept_params["tools"] = list(kept_tools)
         return kept_params
-    for key in _TOOL_SELECTION_PARAMS:
+    dropped_keys: Final = ("tools",) if params.get("functions") else _TOOL_SELECTION_PARAMS
+    for key in dropped_keys:
         _ = kept_params.pop(key, None)
     return kept_params
diff --git a/tests/unit/llms/vertex_ai/gemini/test_vertex_and_google_ai_studio_gemini.py b/tests/unit/llms/vertex_ai/gemini/test_vertex_and_google_ai_studio_gemini.py
index 4faa1ddbfdd..c0219b70cfc 100644
--- a/tests/unit/llms/vertex_ai/gemini/test_vertex_and_google_ai_studio_gemini.py
+++ b/tests/unit/llms/vertex_ai/gemini/test_vertex_and_google_ai_studio_gemini.py
@@ -10721,6 +10721,26 @@ def test_gemini_sends_no_tools_when_drop_params_drops_every_hosted_mcp_tool(monk
     assert "tool_choice" not in mapped
 
 
+@pytest.mark.parametrize(("config_class", "route"), _GEMINI_ROUTES)
+def test_gemini_keeps_tool_choice_none_for_legacy_functions_after_dropping_every_hosted_mcp_tool(
+    monkeypatch, config_class, route
+):
+    monkeypatch.setattr(litellm, "drop_params", False)
+    mapped: Final = config_class().map_openai_params(
+        non_default_params={
+            "tools": [_HOSTED_MCP_TOOL],
+            "functions": [_WEATHER_FUNCTION_TOOL["function"]],
+            "tool_choice": "none",
+        },
+        optional_params={},
+        model="gemini-3.8-flash",
+        drop_params=True,
+    )
+    assert "deepwiki" not in json.dumps(mapped)
+    assert "get_weather" in json.dumps(mapped["tools"])
+    assert mapped["tool_choice"] == {"functionCallingConfig": {"mode": "NONE"}}
+
+
 @pytest.mark.parametrize("chunk_indices", [[0, 1], [2, 1, 0]])
 def test_grounding_support_preserves_every_web_source(chunk_indices: list[int]) -> None:
     metadata: Final = {