diff --git a/litellm/utils.py b/litellm/utils.py
index d9bffd9b92a..252018214d4 100644
--- a/litellm/utils.py
+++ b/litellm/utils.py
@@ -7447,11 +7447,12 @@ def filter_tools_by_allowed_types(
           allowed_tool_types: ["function"]
 
     A tool without a ``type`` key is treated as ``function`` (matching OpenAI
-    defaults). Returns None when no tools survive so an empty ``tools: []``
-    array is not sent upstream (some providers reject that too).
+    defaults). Returns None when no tools survive — including when the incoming
+    list is already empty — so an empty ``tools: []`` array is never sent
+    upstream (some providers reject that too).
     """
     if not tools:
-        return tools
+        return None
     filtered = [
         t
         for t in tools
diff --git a/tests/test_litellm/test_utils.py b/tests/test_litellm/test_utils.py
index baaf421bc0f..7dcce9d7189 100644
--- a/tests/test_litellm/test_utils.py
+++ b/tests/test_litellm/test_utils.py
@@ -4908,7 +4908,8 @@ def test_filter_tools_by_allowed_types_wider_allowlist_and_empty_result() -> Non
     )
 
     assert filter_tools_by_allowed_types(tools=None, allowed_tool_types=["function"]) is None
-    assert filter_tools_by_allowed_types(tools=[], allowed_tool_types=["function"]) == []
+    # an already-empty list is normalized to None too — some providers reject tools: []
+    assert filter_tools_by_allowed_types(tools=[], allowed_tool_types=["function"]) is None
 
 
 def test_reconcile_tool_choice_after_tool_filtering() -> None: