diff --git a/src/Avalonia.Animation/Easing/Easing.cs b/src/Avalonia.Animation/Easing/Easing.cs
index 5b0dea6c60..e006459652 100644
--- a/src/Avalonia.Animation/Easing/Easing.cs
+++ b/src/Avalonia.Animation/Easing/Easing.cs
@@ -1,6 +1,7 @@
 using System;
 using System.Collections.Generic;
 using System.ComponentModel;
+using System.Globalization;
 using System.Linq;
 
 namespace Avalonia.Animation.Easings
@@ -25,6 +26,11 @@ namespace Avalonia.Animation.Easings
         /// <returns>Returns the instance of the parsed type.</returns>
         public static Easing Parse(string e)
         {
+            if (e.Contains(','))
+            {
+                return new SplineEasing(KeySpline.Parse(e, CultureInfo.InvariantCulture));
+            }
+
             if (_easingTypes == null)
             {
                 _easingTypes = new Dictionary<string, Type>();
diff --git a/src/Avalonia.Animation/Easing/SplineEasing.cs b/src/Avalonia.Animation/Easing/SplineEasing.cs
new file mode 100644
index 0000000000..975fcc4746
--- /dev/null
+++ b/src/Avalonia.Animation/Easing/SplineEasing.cs
@@ -0,0 +1,85 @@
+namespace Avalonia.Animation.Easings
+{
+    /// <summary>
+    /// Eases a <see cref="double"/> value
+    /// using a user-defined cubic bezier curve.
+    /// Good for custom easing functions that doesn't quite
+    /// fit with the built-in ones. 
+    /// </summary>
+    public class SplineEasing : Easing
+    {
+        /// <summary>
+        /// X coordinate of the first control point
+        /// </summary>
+        public double X1
+        {
+            get => _internalKeySpline.ControlPointX1;
+            set
+            {
+                _internalKeySpline.ControlPointX1 = value;
+            }
+        }
+
+        /// <summary>
+        /// Y coordinate of the first control point
+        /// </summary>
+        public double Y1
+        {
+            get => _internalKeySpline.ControlPointY1;
+            set
+            {
+                _internalKeySpline.ControlPointY1 = value;
+            }
+        }
+
+        /// <summary>
+        /// X coordinate of the second control point
+        /// </summary> 
+        public double X2
+        {
+            get => _internalKeySpline.ControlPointX2;
+            set
+            {
+                _internalKeySpline.ControlPointX2 = value;
+            }
+        }
+
+        /// <summary>
+        /// Y coordinate of the second control point
+        /// </summary>
+        public double Y2
+        {
+            get => _internalKeySpline.ControlPointY2;
+            set
+            {
+                _internalKeySpline.ControlPointY2 = value;
+            }
+        }
+
+        private readonly KeySpline _internalKeySpline;
+
+        public SplineEasing(double x1 = 0d, double y1 = 0d, double x2 = 1d, double y2 = 1d)
+        {
+            _internalKeySpline = new KeySpline();
+
+            this.X1 = x1;
+            this.Y1 = y1;
+            this.X2 = x2;
+            this.Y1 = y2;
+        }
+
+        public SplineEasing(KeySpline keySpline)
+        {
+            _internalKeySpline = keySpline;
+        }
+        
+        public SplineEasing()
+        {
+            _internalKeySpline = new KeySpline();
+        }
+
+        /// <inheritdoc/>
+        public override double Ease(double progress) =>
+            _internalKeySpline.GetSplineProgress(progress);
+    }
+}
diff --git a/src/Avalonia.Animation/KeySpline.cs b/src/Avalonia.Animation/KeySpline.cs
index 5a4f7a15a3..a6e9769186 100644
--- a/src/Avalonia.Animation/KeySpline.cs
+++ b/src/Avalonia.Animation/KeySpline.cs
@@ -81,7 +81,10 @@ namespace Avalonia.Animation
         /// <returns>A <see cref="KeySpline"/> with the appropriate values set</returns>
         public static KeySpline Parse(string value, CultureInfo culture)
         {
-            using (var tokenizer = new StringTokenizer((string)value, CultureInfo.InvariantCulture, exceptionMessage: "Invalid KeySpline."))
+            if (culture is null)
+                culture = CultureInfo.InvariantCulture;
+
+            using (var tokenizer = new StringTokenizer((string)value, culture, exceptionMessage: $"Invalid KeySpline string: \"{value}\"."))
             {
                 return new KeySpline(tokenizer.ReadDouble(), tokenizer.ReadDouble(), tokenizer.ReadDouble(), tokenizer.ReadDouble());
             }
@@ -98,6 +101,7 @@ namespace Avalonia.Animation
                 if (IsValidXValue(value))
                 {
                     _controlPointX1 = value;
+                    _isDirty = true;
                 }
                 else
                 {
@@ -112,7 +116,11 @@ namespace Avalonia.Animation
         public double ControlPointY1
         {
             get => _controlPointY1;
-            set => _controlPointY1 = value;
+            set
+            {
+                _controlPointY1 = value;
+                _isDirty = true;
+            }
         }
 
         /// <summary>
@@ -126,6 +134,7 @@ namespace Avalonia.Animation
                 if (IsValidXValue(value))
                 {
                     _controlPointX2 = value;
+                    _isDirty = true;
                 }
                 else
                 {
@@ -140,7 +149,11 @@ namespace Avalonia.Animation
         public double ControlPointY2
         {
             get => _controlPointY2;
-            set => _controlPointY2 = value;
+            set
+            {
+                _controlPointY2 = value;
+                _isDirty = true;
+            }
         }
 
         /// <summary>
@@ -330,20 +343,4 @@ namespace Avalonia.Animation
             }
         }
     }
-
-    /// <summary>
-    /// Converts string values to <see cref="KeySpline"/> values
-    /// </summary>
-    public class KeySplineTypeConverter : TypeConverter
-    {
-        public override bool CanConvertFrom(ITypeDescriptorContext context, Type sourceType)
-        {
-            return sourceType == typeof(string);
-        }
-
-        public override object ConvertFrom(ITypeDescriptorContext context, CultureInfo culture, object value)
-        {
-            return KeySpline.Parse((string)value, culture);
-        }
-    }
 }
diff --git a/src/Avalonia.Animation/KeySplineTypeConverter.cs b/src/Avalonia.Animation/KeySplineTypeConverter.cs
new file mode 100644
index 0000000000..cd7427a37d
--- /dev/null
+++ b/src/Avalonia.Animation/KeySplineTypeConverter.cs
@@ -0,0 +1,25 @@
+using System;
+using System.ComponentModel;
+using System.Globalization;
+
+// Ported from WPF open-source code.
+// https://github.com/dotnet/wpf/blob/ae1790531c3b993b56eba8b1f0dd395a3ed7de75/src/Microsoft.DotNet.Wpf/src/PresentationCore/System/Windows/Media/Animation/KeySpline.cs
+
+namespace Avalonia.Animation
+{
+    /// <summary>
+    /// Converts string values to <see cref="KeySpline"/> values
+    /// </summary>
+    public class KeySplineTypeConverter : TypeConverter
+    {
+        public override bool CanConvertFrom(ITypeDescriptorContext context, Type sourceType)
+        {
+            return sourceType == typeof(string);
+        }
+
+        public override object ConvertFrom(ITypeDescriptorContext context, CultureInfo culture, object value)
+        {
+            return KeySpline.Parse((string)value, culture);
+        }
+    }
+}
diff --git a/tests/Avalonia.Animation.UnitTests/KeySplineTests.cs b/tests/Avalonia.Animation.UnitTests/KeySplineTests.cs
index df7c0693e1..fa2ed61e65 100644
--- a/tests/Avalonia.Animation.UnitTests/KeySplineTests.cs
+++ b/tests/Avalonia.Animation.UnitTests/KeySplineTests.cs
@@ -1,4 +1,5 @@
 using System;
+using Avalonia.Animation.Easings;
 using Avalonia.Controls.Shapes;
 using Avalonia.Media;
 using Avalonia.Styling;
@@ -25,6 +26,16 @@ namespace Avalonia.Animation.UnitTests
             Assert.Equal(4, keySpline.ControlPointY2);
         }
 
+        [Theory]
+        [InlineData("1,2F,3,4")] 
+        [InlineData("Foo,Bar,Fee,Buzz")] 
+        public void Can_Handle_Invalid_String_KeySpline_Via_TypeConverter(string input)
+        {
+            var conv = new KeySplineTypeConverter();
+
+            Assert.ThrowsAny<Exception>(() => (KeySpline)conv.ConvertFrom(input));
+        }
+
         [Theory]
         [InlineData(0.00)]
         [InlineData(0.50)]
@@ -46,6 +57,22 @@ namespace Avalonia.Animation.UnitTests
             Assert.Throws<ArgumentException>(() => keySpline.ControlPointX2 = input);
         }
 
+        [Fact]
+        public void SplineEasing_Can_Be_Mutated()
+        {
+            var easing = new SplineEasing();
+
+            Assert.Equal(0, easing.Ease(0));
+            Assert.Equal(1, easing.Ease(1));
+
+            easing.X1 = 0.25;
+            easing.Y1 = 0.5;
+            easing.X2 = 0.75;
+            easing.Y2 = 1.0;
+
+            Assert.NotEqual(0.5, easing.Ease(0.5));
+        }
+
         /*
           To get the test values for the KeySpline test, you can:
           1) Grab the WPF sample for KeySpline animations from https://github.com/microsoft/WPF-Samples/tree/master/Animation/KeySplineAnimations
@@ -141,5 +168,73 @@ namespace Avalonia.Animation.UnitTests
             expected = 1.8016358493761722;
             Assert.True(Math.Abs(rotateTransform.Angle - expected) <= tolerance);
         }
+        
+        [Fact]
+        public void Check_KeySpline_Parsing_Is_Correct()
+        {
+            var keyframe1 = new KeyFrame()
+            {
+                Setters =
+                {
+                    new Setter(RotateTransform.AngleProperty, -2.5d),
+                },
+                KeyTime = TimeSpan.FromSeconds(0)
+            };
+
+            var keyframe2 = new KeyFrame()
+            {
+                Setters =
+                {
+                    new Setter(RotateTransform.AngleProperty, 2.5d),
+                },
+                KeyTime = TimeSpan.FromSeconds(5),
+            };
+
+            var animation = new Animation()
+            {
+                Duration = TimeSpan.FromSeconds(5),
+                Children =
+                {
+                    keyframe1,
+                    keyframe2
+                },
+                IterationCount = new IterationCount(5),
+                PlaybackDirection = PlaybackDirection.Alternate,
+                Easing = Easing.Parse("0.1123555056179775,0.657303370786517,0.8370786516853934,0.499999999999999999")
+            };
+
+            var rotateTransform = new RotateTransform(-2.5);
+            var rect = new Rectangle()
+            {
+                RenderTransform = rotateTransform
+            };
+
+            var clock = new TestClock();
+            var animationRun = animation.RunAsync(rect, clock);
+
+            // position is what you'd expect at end and beginning
+            clock.Step(TimeSpan.Zero);
+            Assert.Equal(rotateTransform.Angle, -2.5);
+            clock.Step(TimeSpan.FromSeconds(5));
+            Assert.Equal(rotateTransform.Angle, 2.5);
+
+            // test some points in between end and beginning
+            var tolerance = 0.01;
+            clock.Step(TimeSpan.Parse("00:00:10.0153932"));
+            var expected = -2.4122350198982545;
+            Assert.True(Math.Abs(rotateTransform.Angle - expected) <= tolerance);
+
+            clock.Step(TimeSpan.Parse("00:00:11.2655407"));
+            expected = -0.37153223002125113;
+            Assert.True(Math.Abs(rotateTransform.Angle - expected) <= tolerance);
+
+            clock.Step(TimeSpan.Parse("00:00:12.6158773"));
+            expected = 0.3967885416786294;
+            Assert.True(Math.Abs(rotateTransform.Angle - expected) <= tolerance);
+
+            clock.Step(TimeSpan.Parse("00:00:14.6495256"));
+            expected = 1.8016358493761722;
+            Assert.True(Math.Abs(rotateTransform.Angle - expected) <= tolerance);
+        }
     }
 }