diff --git a/src/Ursa/Controls/DateTimePicker/DateTimePicker.cs b/src/Ursa/Controls/DateTimePicker/DateTimePicker.cs
index 6c52844..43fafbb 100644
--- a/src/Ursa/Controls/DateTimePicker/DateTimePicker.cs
+++ b/src/Ursa/Controls/DateTimePicker/DateTimePicker.cs
@@ -140,7 +140,7 @@ public class DateTimePicker : DatePickerBase
         }
     }
 
-    private void OnTimeSelectedChanged(object sender, TimeChangedEventArgs e)
+    private void OnTimeSelectedChanged(object? sender, TimeChangedEventArgs e)
     {
         if (SelectedDate is null)
         {
diff --git a/src/Ursa/Controls/DateTimePicker/TimePicker.cs b/src/Ursa/Controls/DateTimePicker/TimePicker.cs
index 5528bdb..3eee8f7 100644
--- a/src/Ursa/Controls/DateTimePicker/TimePicker.cs
+++ b/src/Ursa/Controls/DateTimePicker/TimePicker.cs
@@ -93,7 +93,7 @@ public class TimePicker : TimePickerBase, IClearControl
         SyncTimeToText(SelectedTime);
     }
 
-    private void OnPresenterTimeChanged(object sender, TimeChangedEventArgs e)
+    private void OnPresenterTimeChanged(object? sender, TimeChangedEventArgs e)
     {
         if (_suppressTextPresenterEvent) return;
         SetCurrentValue(SelectedTimeProperty, e.NewTime);
diff --git a/src/Ursa/Controls/DateTimePicker/TimeRangePicker.cs b/src/Ursa/Controls/DateTimePicker/TimeRangePicker.cs
index fae812c..ff0c7c0 100644
--- a/src/Ursa/Controls/DateTimePicker/TimeRangePicker.cs
+++ b/src/Ursa/Controls/DateTimePicker/TimeRangePicker.cs
@@ -156,7 +156,7 @@ public class TimeRangePicker : TimePickerBase, IClearControl
         SyncTimeToText(EndTime, false);
     }
 
-    private void OnPresenterTimeChanged(object sender, TimeChangedEventArgs e)
+    private void OnPresenterTimeChanged(object? sender, TimeChangedEventArgs e)
     {
         if (_suppressTextPresenterEvent) return;
         SetCurrentValue(Equals(sender, _startPresenter) ? StartTimeProperty : EndTimeProperty, e.NewTime);
diff --git a/tests/HeadlessTest.Ursa/Controls/FormTests/Dynamic_Item_Generation/Test.cs b/tests/HeadlessTest.Ursa/Controls/FormTests/Dynamic_Item_Generation/Test.cs
index ed0266e..5566ed4 100644
--- a/tests/HeadlessTest.Ursa/Controls/FormTests/Dynamic_Item_Generation/Test.cs
+++ b/tests/HeadlessTest.Ursa/Controls/FormTests/Dynamic_Item_Generation/Test.cs
@@ -26,6 +26,7 @@ public class Test
         window.Show();
 
         var form = window.FindControl<Form>("Form");
+        Assert.NotNull(form);
         var logicalChildren = form.GetLogicalChildren().ToList();
         Assert.True(logicalChildren.All(a=>a is FormItem));
         Assert.IsType<TextBox>(logicalChildren[0].LogicalChildren[0]);
@@ -65,6 +66,7 @@ public class Test
         window.Show();
 
         var form = window.FindControl<Form>("Form");
+        Assert.NotNull(form);
         var logicalChildren = form.GetLogicalChildren().ToList();
         Assert.True(logicalChildren.All(a=>a is FormGroup));
         var formGroup = (FormGroup)logicalChildren[0];
@@ -108,6 +110,7 @@ public class Test
         window.Show();
 
         var form = window.FindControl<Form>("Form");
+        Assert.NotNull(form);
         var logicalChildren = form.GetLogicalChildren().ToList();
         Assert.True(logicalChildren.All(a=>a is FormItem || a is FormGroup));
         Assert.IsType<TextBox>(logicalChildren[0].LogicalChildren[0]);