diff --git a/appveyor.yml b/appveyor.yml
index 76f991d38e..3c36c2fcd3 100644
--- a/appveyor.yml
+++ b/appveyor.yml
@@ -1,4 +1,4 @@
-os: Visual Studio 2017 RC
+os: Visual Studio 2017
 platform:
 - Any CPU
 configuration:
@@ -11,10 +11,10 @@ environment:
     secure: OtVfyN3ErqQrDTnWH2HDfJDlCiu/i4/X4wFmK3ZXXP7HmCiXYPSbTjMPwwdOxRaK
   MYGET_API_URL: https://www.myget.org/F/avalonia-ci/api/v2/package
 install:
-  - if not exist dotnet-1.0.1.exe appveyor DownloadFile https://go.microsoft.com/fwlink/?linkid=843448 -FileName "dotnet-1.0.1.exe"
   - if not exist gtk-sharp-2.12.26.msi appveyor DownloadFile http://download.xamarin.com/GTKforWindows/Windows/gtk-sharp-2.12.26.msi
-  - msiexec /i gtk-sharp-2.12.26.msi /qn /norestart
-  - cmd: call dotnet-1.0.1.exe /quiet
+  - if not exist dotnet-1.0.1.exe appveyor DownloadFile https://go.microsoft.com/fwlink/?linkid=843448 -FileName "dotnet-1.0.1.exe"
+  - ps: Start-Process -FilePath "msiexec" -ArgumentList "/i gtk-sharp-2.12.26.msi /quiet /qn /norestart" -Wait
+  - ps: Start-Process -FilePath "dotnet-1.0.1.exe" -ArgumentList "/quiet" -Wait
   - cmd: set PATH=%programfiles(x86)%\GtkSharp\2.12\bin\;%PATH%
 before_build:
 - git submodule update --init
diff --git a/src/Avalonia.Visuals/Media/ImageBrush.cs b/src/Avalonia.Visuals/Media/ImageBrush.cs
index 85c1f6c71a..69b98fd35c 100644
--- a/src/Avalonia.Visuals/Media/ImageBrush.cs
+++ b/src/Avalonia.Visuals/Media/ImageBrush.cs
@@ -8,7 +8,7 @@ namespace Avalonia.Media
     /// <summary>
     /// Paints an area with an <see cref="IBitmap"/>.
     /// </summary>
-    public class ImageBrush : TileBrush, IImageBrush
+    public class ImageBrush : TileBrush, IImageBrush, IMutableBrush
     {
         /// <summary>
         /// Defines the <see cref="Visual"/> property.
@@ -17,14 +17,14 @@ namespace Avalonia.Media
             AvaloniaProperty.Register<ImageBrush, IBitmap>("Source");
 
         /// <summary>
-        /// Initializes a new instance of the <see cref="VisualBrush"/> class.
+        /// Initializes a new instance of the <see cref="ImageBrush"/> class.
         /// </summary>
         public ImageBrush()
         {
         }
 
         /// <summary>
-        /// Initializes a new instance of the <see cref="VisualBrush"/> class.
+        /// Initializes a new instance of the <see cref="ImageBrush"/> class.
         /// </summary>
         /// <param name="source">The image to draw.</param>
         public ImageBrush(IBitmap source)
@@ -40,5 +40,11 @@ namespace Avalonia.Media
             get { return GetValue(SourceProperty); }
             set { SetValue(SourceProperty, value); }
         }
+
+        /// <inheritdoc/>
+        IBrush IMutableBrush.ToImmutable()
+        {
+            return new Immutable.ImmutableImageBrush(this);
+        }
     }
 }
diff --git a/src/Avalonia.Visuals/Media/LinearGradientBrush.cs b/src/Avalonia.Visuals/Media/LinearGradientBrush.cs
index 33eea4fbad..6c0d500343 100644
--- a/src/Avalonia.Visuals/Media/LinearGradientBrush.cs
+++ b/src/Avalonia.Visuals/Media/LinearGradientBrush.cs
@@ -6,7 +6,7 @@ namespace Avalonia.Media
     /// <summary>
     /// A brush that draws with a linear gradient.
     /// </summary>
-    public sealed class LinearGradientBrush : GradientBrush, ILinearGradientBrush
+    public sealed class LinearGradientBrush : GradientBrush, ILinearGradientBrush, IMutableBrush
     {
         /// <summary>
         /// Defines the <see cref="StartPoint"/> property.
@@ -41,5 +41,11 @@ namespace Avalonia.Media
             get { return GetValue(EndPointProperty); }
             set { SetValue(EndPointProperty, value); }
         }
+
+        /// <inheritdoc/>
+        IBrush IMutableBrush.ToImmutable()
+        {
+            return new Immutable.ImmutableLinearGradientBrush(this);
+        }
     }
 }
\ No newline at end of file
diff --git a/src/Avalonia.Visuals/Media/RadialGradientBrush.cs b/src/Avalonia.Visuals/Media/RadialGradientBrush.cs
index b721e19138..9f9c2733ec 100644
--- a/src/Avalonia.Visuals/Media/RadialGradientBrush.cs
+++ b/src/Avalonia.Visuals/Media/RadialGradientBrush.cs
@@ -7,7 +7,7 @@ namespace Avalonia.Media
     /// Paints an area with a radial gradient. A focal point defines the beginning of the gradient, 
     /// and a circle defines the end point of the gradient.
     /// </summary>
-    public sealed class RadialGradientBrush : GradientBrush, IRadialGradientBrush
+    public sealed class RadialGradientBrush : GradientBrush, IRadialGradientBrush, IMutableBrush
     {
         /// <summary>
         /// Defines the <see cref="Center"/> property.
@@ -61,5 +61,11 @@ namespace Avalonia.Media
             get { return GetValue(RadiusProperty); }
             set { SetValue(RadiusProperty, value); }
         }
+
+        /// <inheritdoc/>
+        IBrush IMutableBrush.ToImmutable()
+        {
+            return new Immutable.ImmutableRadialGradientBrush(this);
+        }
     }
 }
\ No newline at end of file
diff --git a/src/Avalonia.Visuals/Media/VisualBrush.cs b/src/Avalonia.Visuals/Media/VisualBrush.cs
index 85ccf7afc9..a6d2b8ae8f 100644
--- a/src/Avalonia.Visuals/Media/VisualBrush.cs
+++ b/src/Avalonia.Visuals/Media/VisualBrush.cs
@@ -8,7 +8,7 @@ namespace Avalonia.Media
     /// <summary>
     /// Paints an area with an <see cref="IVisual"/>.
     /// </summary>
-    public class VisualBrush : TileBrush, IVisualBrush
+    public class VisualBrush : TileBrush, IVisualBrush, IMutableBrush
     {
         /// <summary>
         /// Defines the <see cref="Visual"/> property.
@@ -40,5 +40,11 @@ namespace Avalonia.Media
             get { return GetValue(VisualProperty); }
             set { SetValue(VisualProperty, value); }
         }
+
+        /// <inheritdoc/>
+        IBrush IMutableBrush.ToImmutable()
+        {
+            return new Immutable.ImmutableVisualBrush(this);
+        }
     }
 }