diff --git a/lib/workflows/hypervisor_downtime.py b/lib/workflows/hypervisor_downtime.py
index adee8df95..ee1ab2125 100644
--- a/lib/workflows/hypervisor_downtime.py
+++ b/lib/workflows/hypervisor_downtime.py
@@ -31,8 +31,10 @@ def get_number_of_hours(start_dt, end_time_str, duration):
 
     :raises ValueError: if the input string is invalid or contains negative values
     """
-    end_time_str = end_time_str.strip()
-    duration = duration.strip()
+    if end_time_str is not None:
+        end_time_str = end_time_str.strip()
+    if duration is not None:
+        duration = duration.strip()
     if not end_time_str and not duration:
         raise ValueError("Input strings cannot be both empty at the same time")
 
diff --git a/tests/lib/workflows/test_hypervisor_downtimes.py b/tests/lib/workflows/test_hypervisor_downtimes.py
index beb035fa0..6db0fdc57 100644
--- a/tests/lib/workflows/test_hypervisor_downtimes.py
+++ b/tests/lib/workflows/test_hypervisor_downtimes.py
@@ -150,6 +150,18 @@ def test_both_single_space_raise_exception():
         get_number_of_hours(start_dt, " ", " ")
 
 
+def test_none_types_handled_too():
+    """Test that both parameters as None in either field does not raise a ValueError"""
+    start_dt = datetime.datetime.strptime("2024-01-01 10:00", "%Y-%m-%d %H:%M").replace(
+        tzinfo=pytz.utc
+    )
+    result = get_number_of_hours(start_dt, "2024-01-01 11:00", None)
+    assert result == 1
+
+    result = get_number_of_hours(start_dt, None, "1h")
+    assert result == 1
+
+
 def test_both_multiple_spaces_raise_exception():
     """Test that both parameters as multiple spaces raise ValueError"""
     start_dt = datetime.datetime.strptime("2024-01-01 10:00", "%Y-%m-%d %H:%M").replace(