diff --git a/benedict/core/keypaths.py b/benedict/core/keypaths.py
index ca4c9dea..6634cab8 100644
--- a/benedict/core/keypaths.py
+++ b/benedict/core/keypaths.py
@@ -13,8 +13,9 @@ def keypaths(
     indexes: bool = False,
     sort: bool = True,
 ) -> list[str]:
-    separator = separator or "."
-    if not type_util.is_string(separator):
+    if separator is None:
+        separator = "."
+    if not type_util.is_string(separator) or len(separator) == 0:
         raise ValueError("separator argument must be a (non-empty) string.")
     kls = keylists(d, indexes=indexes)
     kps = [separator.join([f"{key}" for key in kl]) for kl in kls]
diff --git a/tests/core/test_keypaths.py b/tests/core/test_keypaths.py
index 5d4faa6f..ceb7afc7 100644
--- a/tests/core/test_keypaths.py
+++ b/tests/core/test_keypaths.py
@@ -106,7 +106,7 @@ def test_keypaths_with_invalid_separator(self) -> None:
         with self.assertRaises(ValueError):
             _ = _keypaths(i, separator=True)  # type: ignore[arg-type]
 
-    def test_keypaths_without_separator(self) -> None:
+    def test_keypaths_with_none_separator(self) -> None:
         i = {
             "a": 1,
             "b": {
@@ -120,9 +120,7 @@ def test_keypaths_without_separator(self) -> None:
                 },
             },
         }
-        # with self.assertRaises(ValueError):
-        #     o = _keypaths(i, separator=None)
-        o = _keypaths(i)
+        o = _keypaths(i, separator=None)
         r = [
             "a",
             "b",