diff --git a/tests/unit/preprocessor/_time/test_time.py b/tests/unit/preprocessor/_time/test_time.py
index b478a97143..8cda75b73b 100644
--- a/tests/unit/preprocessor/_time/test_time.py
+++ b/tests/unit/preprocessor/_time/test_time.py
@@ -170,6 +170,13 @@ def test_extract_time_no_time(self):
         cube = _create_sample_cube()[0]
         sliced = extract_time(cube, 1950, 1, 1, 1950, 12, 31)
         assert cube == sliced
+    
+    def test_extract_time_none_year(self):
+        """Test extract_time when one of the years is None."""
+        cube = self.cube.coord('time').guess_bounds()
+        with assert_raises(ValueError): 
+            extract_time(cube, None, 1, 1, 1950, 2, 1)
+
 
 
 class TestClipTimerange(tests.Test):