diff --git a/pyproject.toml b/pyproject.toml
index 9260894..221aec0 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -4,7 +4,7 @@ build-backend = "hatchling.build"
 
 [project]
 name = "smtpfast"
-version = "0.1.0"
+version = "0.1.1"
 description = "The official Python SDK for the SMTPfast API."
 readme = "README.md"
 license = "MIT"
diff --git a/src/smtpfast/_core.py b/src/smtpfast/_core.py
index 581932b..11aeab1 100644
--- a/src/smtpfast/_core.py
+++ b/src/smtpfast/_core.py
@@ -188,6 +188,9 @@ def __init__(self, core: AsyncCore) -> None:
 
 def _fill(route: str, values: Mapping[str, str] | None) -> str:
     for name, value in (values or {}).items():
+        # "", "." or ".." would become a dot-segment that resolves to another endpoint.
+        if str(value) in ("", ".", ".."):
+            raise SMTPfastError(f"Invalid path parameter {name}: {str(value)!r}")
         route = route.replace("{" + name + "}", quote(str(value), safe=""))
     return route
 
diff --git a/src/smtpfast/_version.py b/src/smtpfast/_version.py
index 3dc1f76..485f44a 100644
--- a/src/smtpfast/_version.py
+++ b/src/smtpfast/_version.py
@@ -1 +1 @@
-__version__ = "0.1.0"
+__version__ = "0.1.1"
diff --git a/tests/test_client.py b/tests/test_client.py
index d4b8ca4..5976168 100644
--- a/tests/test_client.py
+++ b/tests/test_client.py
@@ -31,6 +31,14 @@ def test_path_params_are_encoded():
     assert rec.calls[0].url.raw_path.decode() == "/api/v1/inboxes/in%201/threads/th_2/emails/em%2F3/reply"
 
 
+def test_empty_or_dot_path_params_are_rejected():
+    client, rec = make()
+    for bad in ("", ".", ".."):
+        with pytest.raises(smtpfast.SMTPfastError):
+            client.emails.get(bad)
+    assert rec.calls == []
+
+
 def test_query_params_skip_none_and_format_bools():
     client, rec = make([ok({"data": [], "has_more": False})])
     client.contacts.list(limit=5, disposable=False)