diff --git a/src/undate/undate.py b/src/undate/undate.py
index 1b9671e..d3891ad 100644
--- a/src/undate/undate.py
+++ b/src/undate/undate.py
@@ -365,7 +365,7 @@ def __contains__(self, other: object) -> bool:
 
     @classmethod
     def to_undate(cls, other: object) -> "Undate":
-        """Converted arbitrary object to Undate, if possible. Raises TypeError
+        """Convert arbitrary object to Undate, if possible. Raises TypeError
         if conversion is not possible.
 
         Currently suppports:
@@ -377,6 +377,9 @@ def to_undate(cls, other: object) -> "Undate":
                 return other
             case datetime.date() | datetime.datetime():
                 return Undate(other.year, other.month, other.day)
+            case Date():
+                # handle conversion from internal Date class
+                return Undate(other.year, other.month, other.day)
 
             case _:
                 raise TypeError(f"Conversion from {type(other)} is not supported")
diff --git a/tests/test_undate.py b/tests/test_undate.py
index a9087c2..7a140df 100644
--- a/tests/test_undate.py
+++ b/tests/test_undate.py
@@ -4,7 +4,7 @@
 
 from undate import Undate, UndateInterval, Calendar
 from undate.converters.base import BaseCalendarConverter
-from undate.date import DatePrecision, Timedelta
+from undate.date import Date, DatePrecision, Timedelta
 
 
 class TestUndate:
@@ -152,6 +152,14 @@ def test_to_undate(self):
         assert isinstance(undate_from_dt, Undate)
         assert undate_from_dt == Undate(now.year, now.month, now.day)
 
+        # from internal Date object
+        y2k = Date(2000)
+        y2k_to_undate = Undate.to_undate(y2k)
+        assert isinstance(y2k_to_undate, Undate)
+        assert int(y2k_to_undate.year) == y2k.year
+        assert y2k_to_undate.month is None
+        assert y2k_to_undate.day is None
+
         # unsupported type
         with pytest.raises(TypeError):
             Undate.to_undate("foo")