diff --git a/src/openai/_qs.py b/src/openai/_qs.py
index 4127c19c62..d3c34ce6b0 100644
--- a/src/openai/_qs.py
+++ b/src/openai/_qs.py
@@ -112,10 +112,9 @@ def _stringify_item(
                     f"Unknown array_format value: {array_format}, choose from {', '.join(get_args(ArrayFormat))}"
                 )
 
-        serialised = self._primitive_value_to_str(value)
-        if not serialised:
+        if value is None:
             return []
-        return [(key, serialised)]
+        return [(key, self._primitive_value_to_str(value))]
 
     def _primitive_value_to_str(self, value: PrimitiveData) -> str:
         # copied from httpx
diff --git a/tests/test_qs.py b/tests/test_qs.py
index 697b8a95ec..dc5fd979c6 100644
--- a/tests/test_qs.py
+++ b/tests/test_qs.py
@@ -22,6 +22,14 @@ def test_basic() -> None:
     assert stringify({"a": None}) == ""
 
 
+def test_empty_string_scalar_is_kept_distinct_from_none() -> None:
+    # An explicit empty string is a real value ("a=") and must not be
+    # conflated with omitting the key entirely (None).
+    assert unquote(stringify({"a": ""})) == "a="
+    assert stringify({"a": None}) == ""
+    assert unquote(stringify({"a": "", "b": 1})) == "a=&b=1"
+
+
 @pytest.mark.parametrize("method", ["class", "function"])
 def test_nested_dotted(method: str) -> None:
     if method == "class":