diff --git a/news/938.documentation.1 b/news/938.documentation.1
new file mode 100644
index 000000000..950044714
--- /dev/null
+++ b/news/938.documentation.1
@@ -0,0 +1 @@
+Added argument and return type hints to :meth:`~icalendar.cal.timezone.Timezone._make_unique_tzname`. Located an untyped helper and confirm its call sites in ``get_transitions``. @kdaanish866
diff --git a/src/icalendar/cal/timezone.py b/src/icalendar/cal/timezone.py
index 65881e264..16510a171 100644
--- a/src/icalendar/cal/timezone.py
+++ b/src/icalendar/cal/timezone.py
@@ -132,7 +132,7 @@ def _extract_offsets(component: TimezoneDaylight | TimezoneStandard, tzname: str
         return is_dst, transitions
 
     @staticmethod
-    def _make_unique_tzname(tzname, tznames):
+    def _make_unique_tzname(tzname: str, tznames: set[str]) -> str:
         """
         :param tzname: Candidate tzname
         :param tznames: Other tznames