diff --git a/fixedcal/core/date.py b/fixedcal/core/date.py
index e614f64..6f3a99f 100644
--- a/fixedcal/core/date.py
+++ b/fixedcal/core/date.py
@@ -20,9 +20,9 @@ class FixedDate:
                 date: datetime.date = None,
                 day_of_year: int = None,
                 year: int = None) -> None:
-        if date is not None:
+        if isinstance(date, datetime.date):
             init_tuple = self._from_datetime(date)
-        elif day_of_year is not None and year is not None:
+        elif isinstance(day_of_year, int) and isinstance(year, int):
             init_tuple = self._from_day_of_year(day_of_year, year)
         else:
             raise ValueError("Invalid FixedDate initialization")
diff --git a/tests/basic_datetime_test.py b/tests/basic_datetime_test.py
index 0954922..7cec911 100644
--- a/tests/basic_datetime_test.py
+++ b/tests/basic_datetime_test.py
@@ -80,3 +80,10 @@ class TestBasicDateInit(unittest.TestCase):
     def test_today(self):
         fixed_date_datetime = FixedDate.today().date
         self.assertEqual(fixed_date_datetime, datetime.date.today())
+
+    def test_init_with_invalid_parameter_type(self):
+        self.assertRaises(ValueError, lambda : FixedDate(date="today"))
+
+    def test_init_with_invalid_parameter_combination(self):
+        # day_of_year also requires year parameter
+        self.assertRaises(ValueError, lambda : FixedDate(day_of_year=15))
diff --git a/tests/operations_test.py b/tests/operations_test.py
index 46142fb..28582ef 100644
--- a/tests/operations_test.py
+++ b/tests/operations_test.py
@@ -16,6 +16,10 @@ class TestOperations(unittest.TestCase):
     def test_greather_than_with_true_expected(self):
         self.assertTrue(self.fixed2 > self.fixed1)
 
+    def test_greather_than_with_different_years(self):
+        another_year = FixedDate(date=datetime.date(2023, 12, 5))
+        self.assertTrue(another_year > self.fixed1)
+
     def test_greather_than_with_false_expected(self):
         self.assertFalse(self.fixed1 > self.fixed2)