diff --git a/src/anthropic/_qs.py b/src/anthropic/_qs.py
index 4127c19c..d8cedf44 100644
--- a/src/anthropic/_qs.py
+++ b/src/anthropic/_qs.py
@@ -85,12 +85,10 @@ def _stringify_item(
         if isinstance(value, (list, tuple)):
             array_format = opts.array_format
             if array_format == "comma":
-                return [
-                    (
-                        key,
-                        ",".join(self._primitive_value_to_str(item) for item in value if item is not None),
-                    ),
-                ]
+                serialised = ",".join(self._primitive_value_to_str(item) for item in value if item is not None)
+                if not serialised:
+                    return []
+                return [(key, serialised)]
             elif array_format == "repeat":
                 items = []
                 for item in value:
diff --git a/tests/test_qs.py b/tests/test_qs.py
index 564a41e6..5b0845e2 100644
--- a/tests/test_qs.py
+++ b/tests/test_qs.py
@@ -52,6 +52,9 @@ def test_array_comma(method: str) -> None:
     assert unquote(serialise({"in": ["foo", "bar"]})) == "in=foo,bar"
     assert unquote(serialise({"a": {"b": [True, False]}})) == "a[b]=true,false"
     assert unquote(serialise({"a": {"b": [True, False, None, True]}})) == "a[b]=true,false,true"
+    assert unquote(serialise({"a": []})) == ""
+    assert unquote(serialise({"a": [None]})) == ""
+    assert unquote(serialise({"a": {"b": []}})) == ""
 
 
 def test_array_repeat() -> None: