diff --git a/benedict/core/keypaths.py b/benedict/core/keypaths.py
index 6634cab..ddd9c1e 100644
--- a/benedict/core/keypaths.py
+++ b/benedict/core/keypaths.py
@@ -13,9 +13,8 @@ def keypaths(
     indexes: bool = False,
     sort: bool = True,
 ) -> list[str]:
-    if separator is None:
-        separator = "."
-    if not type_util.is_string(separator) or len(separator) == 0:
+    separator = "." if separator is None else separator
+    if not type_util.is_string(separator) or not separator:
         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 ceb7afc..043da78 100644
--- a/tests/core/test_keypaths.py
+++ b/tests/core/test_keypaths.py
@@ -106,7 +106,11 @@ def test_keypaths_with_invalid_separator(self) -> None:
         with self.assertRaises(ValueError):
             _ = _keypaths(i, separator=True)  # type: ignore[arg-type]
 
-    def test_keypaths_with_none_separator(self) -> None:
+    def test_keypaths_with_empty_separator(self) -> None:
+        with self.assertRaises(ValueError):
+            _ = _keypaths({"a": {"b": 1}}, separator="")
+
+    def test_keypaths_without_separator(self) -> None:
         i = {
             "a": 1,
             "b": {