no boxing required.

src/Avalonia.Animation/AnimationInstance`1.cs

@@ -12,7 +12,7 @@ namespace Avalonia.Animation
     /// Handles interpolation and time-related functions 
     /// for keyframe animations.
     /// </summary>
-    internal class AnimationInstance<T> : SingleSubscriberObservableBase<object>
+    internal class AnimationInstance<T> : SingleSubscriberObservableBase<T>
     {
         private T _lastInterpValue;
         private T _firstKFValue;

src/Avalonia.Animation/Animators/Animator`1.cs

@@ -104,6 +104,11 @@ namespace Avalonia.Animation.Animators
             throw new Exception("Index time is out of keyframe time range.");
         }
 
+        public virtual IDisposable BindAnimation(Animatable control, IObservable<T> instance)
+        {
+            return control.Bind((AvaloniaProperty<T>)Property, instance, BindingPriority.Animation);
+        }
+
         /// <summary>
         /// Runs the KeyFrames Animation.
         /// </summary>
@@ -116,7 +121,8 @@ namespace Avalonia.Animation.Animators
                 clock ?? control.Clock ?? Clock.GlobalClock,
                 onComplete,
                 InterpolationHandler);
-            return control.Bind(Property, instance, BindingPriority.Animation);
+            
+            return BindAnimation(control, instance);
         }
 
         /// <summary>

src/Avalonia.Visuals/Animation/Animators/SolidColorBrushAnimator.cs

@@ -1,4 +1,5 @@
 using System;
+using Avalonia.Data;
 using Avalonia.Media;
 using Avalonia.Media.Immutable;
 
@@ -13,6 +14,11 @@ namespace Avalonia.Animation.Animators
         {
             return new ImmutableSolidColorBrush(ColorAnimator.InterpolateCore(progress, oldValue.Color, newValue.Color));
         }
+
+        public override IDisposable BindAnimation(Animatable control, IObservable<ISolidColorBrush> instance)
+        {
+            return control.Bind((AvaloniaProperty<IBrush>)Property, instance, BindingPriority.Animation);
+        }
     }
     
     [Obsolete]