diff --git a/src/ReactiveUI.Tests/API/ApiApprovalTests.ReactiveUI.net472.approved.txt b/src/ReactiveUI.Tests/API/ApiApprovalTests.ReactiveUI.net472.approved.txt
index c1e244b05b..d4a511ec6d 100644
--- a/src/ReactiveUI.Tests/API/ApiApprovalTests.ReactiveUI.net472.approved.txt
+++ b/src/ReactiveUI.Tests/API/ApiApprovalTests.ReactiveUI.net472.approved.txt
@@ -68,15 +68,15 @@ namespace ReactiveUI
     }
     public static class CommandBinder
     {
-        public static ReactiveUI.IReactiveBinding<TView, TProp> BindCommand<TView, TViewModel, TProp, TControl>(this TView view, TViewModel viewModel, System.Linq.Expressions.Expression<System.Func<TViewModel, TProp>> propertyName, System.Linq.Expressions.Expression<System.Func<TView, TControl>> controlName, string? toEvent = null)
+        public static ReactiveUI.IReactiveBinding<TView, TProp> BindCommand<TView, TViewModel, TProp, TControl>(this TView view, TViewModel? viewModel, System.Linq.Expressions.Expression<System.Func<TViewModel, TProp>> propertyName, System.Linq.Expressions.Expression<System.Func<TView, TControl>> controlName, string? toEvent = null)
             where TView :  class, ReactiveUI.IViewFor<TViewModel>
             where TViewModel :  class
             where TProp : System.Windows.Input.ICommand { }
-        public static ReactiveUI.IReactiveBinding<TView, TProp> BindCommand<TView, TViewModel, TProp, TControl, TParam>(this TView view, TViewModel viewModel, System.Linq.Expressions.Expression<System.Func<TViewModel, TProp>> propertyName, System.Linq.Expressions.Expression<System.Func<TView, TControl>> controlName, System.IObservable<TParam> withParameter, string? toEvent = null)
+        public static ReactiveUI.IReactiveBinding<TView, TProp> BindCommand<TView, TViewModel, TProp, TControl, TParam>(this TView view, TViewModel? viewModel, System.Linq.Expressions.Expression<System.Func<TViewModel, TProp>> propertyName, System.Linq.Expressions.Expression<System.Func<TView, TControl>> controlName, System.IObservable<TParam> withParameter, string? toEvent = null)
             where TView :  class, ReactiveUI.IViewFor<TViewModel>
             where TViewModel :  class
             where TProp : System.Windows.Input.ICommand { }
-        public static ReactiveUI.IReactiveBinding<TView, TProp> BindCommand<TView, TViewModel, TProp, TControl, TParam>(this TView view, TViewModel viewModel, System.Linq.Expressions.Expression<System.Func<TViewModel, TProp>> propertyName, System.Linq.Expressions.Expression<System.Func<TView, TControl>> controlName, System.Linq.Expressions.Expression<System.Func<TViewModel, TParam>> withParameter, string? toEvent = null)
+        public static ReactiveUI.IReactiveBinding<TView, TProp> BindCommand<TView, TViewModel, TProp, TControl, TParam>(this TView view, TViewModel? viewModel, System.Linq.Expressions.Expression<System.Func<TViewModel, TProp>> propertyName, System.Linq.Expressions.Expression<System.Func<TView, TControl>> controlName, System.Linq.Expressions.Expression<System.Func<TViewModel, TParam>> withParameter, string? toEvent = null)
             where TView :  class, ReactiveUI.IViewFor<TViewModel>
             where TViewModel :  class
             where TProp : System.Windows.Input.ICommand { }
@@ -84,11 +84,11 @@ namespace ReactiveUI
     public class CommandBinderImplementation : Splat.IEnableLogger
     {
         public CommandBinderImplementation() { }
-        public ReactiveUI.IReactiveBinding<TView, TProp> BindCommand<TView, TViewModel, TProp, TControl, TParam>(TViewModel viewModel, TView view, System.Linq.Expressions.Expression<System.Func<TViewModel, TProp>> vmProperty, System.Linq.Expressions.Expression<System.Func<TView, TControl>> controlProperty, System.Func<TParam> withParameter, string? toEvent = null)
+        public ReactiveUI.IReactiveBinding<TView, TProp> BindCommand<TView, TViewModel, TProp, TControl, TParam>(TViewModel? viewModel, TView view, System.Linq.Expressions.Expression<System.Func<TViewModel, TProp>> vmProperty, System.Linq.Expressions.Expression<System.Func<TView, TControl>> controlProperty, System.Func<TParam> withParameter, string? toEvent = null)
             where TView :  class, ReactiveUI.IViewFor<TViewModel>
             where TViewModel :  class
             where TProp : System.Windows.Input.ICommand { }
-        public ReactiveUI.IReactiveBinding<TView, TProp> BindCommand<TView, TViewModel, TProp, TControl, TParam>(TViewModel viewModel, TView view, System.Linq.Expressions.Expression<System.Func<TViewModel, TProp>> vmProperty, System.Linq.Expressions.Expression<System.Func<TView, TControl>> controlProperty, System.IObservable<TParam> withParameter, string? toEvent = null)
+        public ReactiveUI.IReactiveBinding<TView, TProp> BindCommand<TView, TViewModel, TProp, TControl, TParam>(TViewModel? viewModel, TView view, System.Linq.Expressions.Expression<System.Func<TViewModel, TProp>> vmProperty, System.Linq.Expressions.Expression<System.Func<TView, TControl>> controlProperty, System.IObservable<TParam> withParameter, string? toEvent = null)
             where TView :  class, ReactiveUI.IViewFor<TViewModel>
             where TViewModel :  class
             where TProp : System.Windows.Input.ICommand { }
diff --git a/src/ReactiveUI.Tests/API/ApiApprovalTests.ReactiveUI.net5.0.approved.txt b/src/ReactiveUI.Tests/API/ApiApprovalTests.ReactiveUI.net5.0.approved.txt
index 3154b3f96c..bd6ceac01d 100644
--- a/src/ReactiveUI.Tests/API/ApiApprovalTests.ReactiveUI.net5.0.approved.txt
+++ b/src/ReactiveUI.Tests/API/ApiApprovalTests.ReactiveUI.net5.0.approved.txt
@@ -70,15 +70,15 @@ namespace ReactiveUI
     }
     public static class CommandBinder
     {
-        public static ReactiveUI.IReactiveBinding<TView, TProp> BindCommand<TView, TViewModel, TProp, TControl>(this TView view, TViewModel viewModel, System.Linq.Expressions.Expression<System.Func<TViewModel, TProp>> propertyName, System.Linq.Expressions.Expression<System.Func<TView, TControl>> controlName, string? toEvent = null)
+        public static ReactiveUI.IReactiveBinding<TView, TProp> BindCommand<TView, TViewModel, TProp, TControl>(this TView view, TViewModel? viewModel, System.Linq.Expressions.Expression<System.Func<TViewModel, TProp>> propertyName, System.Linq.Expressions.Expression<System.Func<TView, TControl>> controlName, string? toEvent = null)
             where TView :  class, ReactiveUI.IViewFor<TViewModel>
             where TViewModel :  class
             where TProp : System.Windows.Input.ICommand { }
-        public static ReactiveUI.IReactiveBinding<TView, TProp> BindCommand<TView, TViewModel, TProp, TControl, TParam>(this TView view, TViewModel viewModel, System.Linq.Expressions.Expression<System.Func<TViewModel, TProp>> propertyName, System.Linq.Expressions.Expression<System.Func<TView, TControl>> controlName, System.IObservable<TParam> withParameter, string? toEvent = null)
+        public static ReactiveUI.IReactiveBinding<TView, TProp> BindCommand<TView, TViewModel, TProp, TControl, TParam>(this TView view, TViewModel? viewModel, System.Linq.Expressions.Expression<System.Func<TViewModel, TProp>> propertyName, System.Linq.Expressions.Expression<System.Func<TView, TControl>> controlName, System.IObservable<TParam> withParameter, string? toEvent = null)
             where TView :  class, ReactiveUI.IViewFor<TViewModel>
             where TViewModel :  class
             where TProp : System.Windows.Input.ICommand { }
-        public static ReactiveUI.IReactiveBinding<TView, TProp> BindCommand<TView, TViewModel, TProp, TControl, TParam>(this TView view, TViewModel viewModel, System.Linq.Expressions.Expression<System.Func<TViewModel, TProp>> propertyName, System.Linq.Expressions.Expression<System.Func<TView, TControl>> controlName, System.Linq.Expressions.Expression<System.Func<TViewModel, TParam>> withParameter, string? toEvent = null)
+        public static ReactiveUI.IReactiveBinding<TView, TProp> BindCommand<TView, TViewModel, TProp, TControl, TParam>(this TView view, TViewModel? viewModel, System.Linq.Expressions.Expression<System.Func<TViewModel, TProp>> propertyName, System.Linq.Expressions.Expression<System.Func<TView, TControl>> controlName, System.Linq.Expressions.Expression<System.Func<TViewModel, TParam>> withParameter, string? toEvent = null)
             where TView :  class, ReactiveUI.IViewFor<TViewModel>
             where TViewModel :  class
             where TProp : System.Windows.Input.ICommand { }
@@ -86,11 +86,11 @@ namespace ReactiveUI
     public class CommandBinderImplementation : Splat.IEnableLogger
     {
         public CommandBinderImplementation() { }
-        public ReactiveUI.IReactiveBinding<TView, TProp> BindCommand<TView, TViewModel, TProp, TControl, TParam>(TViewModel viewModel, TView view, System.Linq.Expressions.Expression<System.Func<TViewModel, TProp>> vmProperty, System.Linq.Expressions.Expression<System.Func<TView, TControl>> controlProperty, System.Func<TParam> withParameter, string? toEvent = null)
+        public ReactiveUI.IReactiveBinding<TView, TProp> BindCommand<TView, TViewModel, TProp, TControl, TParam>(TViewModel? viewModel, TView view, System.Linq.Expressions.Expression<System.Func<TViewModel, TProp>> vmProperty, System.Linq.Expressions.Expression<System.Func<TView, TControl>> controlProperty, System.Func<TParam> withParameter, string? toEvent = null)
             where TView :  class, ReactiveUI.IViewFor<TViewModel>
             where TViewModel :  class
             where TProp : System.Windows.Input.ICommand { }
-        public ReactiveUI.IReactiveBinding<TView, TProp> BindCommand<TView, TViewModel, TProp, TControl, TParam>(TViewModel viewModel, TView view, System.Linq.Expressions.Expression<System.Func<TViewModel, TProp>> vmProperty, System.Linq.Expressions.Expression<System.Func<TView, TControl>> controlProperty, System.IObservable<TParam> withParameter, string? toEvent = null)
+        public ReactiveUI.IReactiveBinding<TView, TProp> BindCommand<TView, TViewModel, TProp, TControl, TParam>(TViewModel? viewModel, TView view, System.Linq.Expressions.Expression<System.Func<TViewModel, TProp>> vmProperty, System.Linq.Expressions.Expression<System.Func<TView, TControl>> controlProperty, System.IObservable<TParam> withParameter, string? toEvent = null)
             where TView :  class, ReactiveUI.IViewFor<TViewModel>
             where TViewModel :  class
             where TProp : System.Windows.Input.ICommand { }
diff --git a/src/ReactiveUI.Tests/API/ApiApprovalTests.ReactiveUI.netcoreapp3.1.approved.txt b/src/ReactiveUI.Tests/API/ApiApprovalTests.ReactiveUI.netcoreapp3.1.approved.txt
index 0ca16ef123..20ce1ee2ca 100644
--- a/src/ReactiveUI.Tests/API/ApiApprovalTests.ReactiveUI.netcoreapp3.1.approved.txt
+++ b/src/ReactiveUI.Tests/API/ApiApprovalTests.ReactiveUI.netcoreapp3.1.approved.txt
@@ -68,15 +68,15 @@ namespace ReactiveUI
     }
     public static class CommandBinder
     {
-        public static ReactiveUI.IReactiveBinding<TView, TProp> BindCommand<TView, TViewModel, TProp, TControl>(this TView view, TViewModel viewModel, System.Linq.Expressions.Expression<System.Func<TViewModel, TProp>> propertyName, System.Linq.Expressions.Expression<System.Func<TView, TControl>> controlName, string? toEvent = null)
+        public static ReactiveUI.IReactiveBinding<TView, TProp> BindCommand<TView, TViewModel, TProp, TControl>(this TView view, TViewModel? viewModel, System.Linq.Expressions.Expression<System.Func<TViewModel, TProp>> propertyName, System.Linq.Expressions.Expression<System.Func<TView, TControl>> controlName, string? toEvent = null)
             where TView :  class, ReactiveUI.IViewFor<TViewModel>
             where TViewModel :  class
             where TProp : System.Windows.Input.ICommand { }
-        public static ReactiveUI.IReactiveBinding<TView, TProp> BindCommand<TView, TViewModel, TProp, TControl, TParam>(this TView view, TViewModel viewModel, System.Linq.Expressions.Expression<System.Func<TViewModel, TProp>> propertyName, System.Linq.Expressions.Expression<System.Func<TView, TControl>> controlName, System.IObservable<TParam> withParameter, string? toEvent = null)
+        public static ReactiveUI.IReactiveBinding<TView, TProp> BindCommand<TView, TViewModel, TProp, TControl, TParam>(this TView view, TViewModel? viewModel, System.Linq.Expressions.Expression<System.Func<TViewModel, TProp>> propertyName, System.Linq.Expressions.Expression<System.Func<TView, TControl>> controlName, System.IObservable<TParam> withParameter, string? toEvent = null)
             where TView :  class, ReactiveUI.IViewFor<TViewModel>
             where TViewModel :  class
             where TProp : System.Windows.Input.ICommand { }
-        public static ReactiveUI.IReactiveBinding<TView, TProp> BindCommand<TView, TViewModel, TProp, TControl, TParam>(this TView view, TViewModel viewModel, System.Linq.Expressions.Expression<System.Func<TViewModel, TProp>> propertyName, System.Linq.Expressions.Expression<System.Func<TView, TControl>> controlName, System.Linq.Expressions.Expression<System.Func<TViewModel, TParam>> withParameter, string? toEvent = null)
+        public static ReactiveUI.IReactiveBinding<TView, TProp> BindCommand<TView, TViewModel, TProp, TControl, TParam>(this TView view, TViewModel? viewModel, System.Linq.Expressions.Expression<System.Func<TViewModel, TProp>> propertyName, System.Linq.Expressions.Expression<System.Func<TView, TControl>> controlName, System.Linq.Expressions.Expression<System.Func<TViewModel, TParam>> withParameter, string? toEvent = null)
             where TView :  class, ReactiveUI.IViewFor<TViewModel>
             where TViewModel :  class
             where TProp : System.Windows.Input.ICommand { }
@@ -84,11 +84,11 @@ namespace ReactiveUI
     public class CommandBinderImplementation : Splat.IEnableLogger
     {
         public CommandBinderImplementation() { }
-        public ReactiveUI.IReactiveBinding<TView, TProp> BindCommand<TView, TViewModel, TProp, TControl, TParam>(TViewModel viewModel, TView view, System.Linq.Expressions.Expression<System.Func<TViewModel, TProp>> vmProperty, System.Linq.Expressions.Expression<System.Func<TView, TControl>> controlProperty, System.Func<TParam> withParameter, string? toEvent = null)
+        public ReactiveUI.IReactiveBinding<TView, TProp> BindCommand<TView, TViewModel, TProp, TControl, TParam>(TViewModel? viewModel, TView view, System.Linq.Expressions.Expression<System.Func<TViewModel, TProp>> vmProperty, System.Linq.Expressions.Expression<System.Func<TView, TControl>> controlProperty, System.Func<TParam> withParameter, string? toEvent = null)
             where TView :  class, ReactiveUI.IViewFor<TViewModel>
             where TViewModel :  class
             where TProp : System.Windows.Input.ICommand { }
-        public ReactiveUI.IReactiveBinding<TView, TProp> BindCommand<TView, TViewModel, TProp, TControl, TParam>(TViewModel viewModel, TView view, System.Linq.Expressions.Expression<System.Func<TViewModel, TProp>> vmProperty, System.Linq.Expressions.Expression<System.Func<TView, TControl>> controlProperty, System.IObservable<TParam> withParameter, string? toEvent = null)
+        public ReactiveUI.IReactiveBinding<TView, TProp> BindCommand<TView, TViewModel, TProp, TControl, TParam>(TViewModel? viewModel, TView view, System.Linq.Expressions.Expression<System.Func<TViewModel, TProp>> vmProperty, System.Linq.Expressions.Expression<System.Func<TView, TControl>> controlProperty, System.IObservable<TParam> withParameter, string? toEvent = null)
             where TView :  class, ReactiveUI.IViewFor<TViewModel>
             where TViewModel :  class
             where TProp : System.Windows.Input.ICommand { }
diff --git a/src/ReactiveUI.Tests/Platforms/wpf/Mocks/FakeXamlCommandBindingView.cs b/src/ReactiveUI.Tests/Platforms/wpf/Mocks/FakeXamlCommandBindingView.cs
index b6854eeda9..234f988f0c 100644
--- a/src/ReactiveUI.Tests/Platforms/wpf/Mocks/FakeXamlCommandBindingView.cs
+++ b/src/ReactiveUI.Tests/Platforms/wpf/Mocks/FakeXamlCommandBindingView.cs
@@ -24,7 +24,7 @@ public FakeXamlCommandBindingView()
         {
             _buttonDeclaredInXaml = new Button();
 
-            this.BindCommand(ViewModel!, vm => vm!.Command2!, v => v._buttonDeclaredInXaml);
+            this.BindCommand(ViewModel, vm => vm!.Command2!, v => v._buttonDeclaredInXaml);
         }
 
         /// <summary>
diff --git a/src/ReactiveUI/Bindings/Command/CommandBinder.cs b/src/ReactiveUI/Bindings/Command/CommandBinder.cs
index fbe6ea0912..d53349f596 100644
--- a/src/ReactiveUI/Bindings/Command/CommandBinder.cs
+++ b/src/ReactiveUI/Bindings/Command/CommandBinder.cs
@@ -48,7 +48,7 @@ static CommandBinder()
         /// important to dispose the binding when the view is deactivated.</param>
         public static IReactiveBinding<TView, TProp> BindCommand<TView, TViewModel, TProp, TControl, TParam>(
                 this TView view,
-                TViewModel viewModel,
+                TViewModel? viewModel,
                 Expression<Func<TViewModel, TProp>> propertyName,
                 Expression<Func<TView, TControl>> controlName,
                 IObservable<TParam> withParameter,
@@ -78,7 +78,7 @@ public static IReactiveBinding<TView, TProp> BindCommand<TView, TViewModel, TPro
         /// important to dispose the binding when the view is deactivated.</param>
         public static IReactiveBinding<TView, TProp> BindCommand<TView, TViewModel, TProp, TControl>(
                 this TView view,
-                TViewModel viewModel,
+                TViewModel? viewModel,
                 Expression<Func<TViewModel, TProp>> propertyName,
                 Expression<Func<TView, TControl>> controlName,
                 string? toEvent = null)
@@ -110,7 +110,7 @@ public static IReactiveBinding<TView, TProp> BindCommand<TView, TViewModel, TPro
         /// important to dispose the binding when the view is deactivated.</param>
         public static IReactiveBinding<TView, TProp> BindCommand<TView, TViewModel, TProp, TControl, TParam>(
                 this TView view,
-                TViewModel viewModel,
+                TViewModel? viewModel,
                 Expression<Func<TViewModel, TProp>> propertyName,
                 Expression<Func<TView, TControl>> controlName,
                 Expression<Func<TViewModel, TParam>> withParameter,
diff --git a/src/ReactiveUI/Bindings/Command/CommandBinderImplementation.cs b/src/ReactiveUI/Bindings/Command/CommandBinderImplementation.cs
index 094e073491..b80db1dd2b 100644
--- a/src/ReactiveUI/Bindings/Command/CommandBinderImplementation.cs
+++ b/src/ReactiveUI/Bindings/Command/CommandBinderImplementation.cs
@@ -38,7 +38,7 @@ public class CommandBinderImplementation : ICommandBinderImplementation
         /// <returns>A class representing the binding. Dispose it to disconnect
         /// the binding.</returns>
         public IReactiveBinding<TView, TProp> BindCommand<TView, TViewModel, TProp, TControl, TParam>(
-                TViewModel viewModel,
+                TViewModel? viewModel,
                 TView view,
                 Expression<Func<TViewModel, TProp>> vmProperty,
                 Expression<Func<TView, TControl>> controlProperty,
@@ -103,7 +103,7 @@ public IReactiveBinding<TView, TProp> BindCommand<TView, TViewModel, TProp, TCon
         /// NOTE: If this parameter is used inside WhenActivated, it's
         /// important to dispose the binding when the view is deactivated.</param>
         public IReactiveBinding<TView, TProp> BindCommand<TView, TViewModel, TProp, TControl, TParam>(
-                TViewModel viewModel,
+                TViewModel? viewModel,
                 TView view,
                 Expression<Func<TViewModel, TProp>> vmProperty,
                 Expression<Func<TView, TControl>> controlProperty,
diff --git a/src/ReactiveUI/Bindings/Command/CommandBinderImplementationMixins.cs b/src/ReactiveUI/Bindings/Command/CommandBinderImplementationMixins.cs
index 1d513cc15b..27a49b45d9 100644
--- a/src/ReactiveUI/Bindings/Command/CommandBinderImplementationMixins.cs
+++ b/src/ReactiveUI/Bindings/Command/CommandBinderImplementationMixins.cs
@@ -17,7 +17,7 @@ internal static class CommandBinderImplementationMixins
     {
         public static IReactiveBinding<TView, TProp> BindCommand<TView, TViewModel, TProp, TControl>(
                 this ICommandBinderImplementation @this,
-                TViewModel viewModel,
+                TViewModel? viewModel,
                 TView view,
                 Expression<Func<TViewModel, TProp>> propertyName,
                 Expression<Func<TView, TControl>> controlName,
@@ -29,7 +29,7 @@ public static IReactiveBinding<TView, TProp> BindCommand<TView, TViewModel, TPro
 
         public static IReactiveBinding<TView, TProp> BindCommand<TView, TViewModel, TProp, TControl, TParam>(
                 this ICommandBinderImplementation @this,
-                TViewModel viewModel,
+                TViewModel? viewModel,
                 TView view,
                 Expression<Func<TViewModel, TProp>> propertyName,
                 Expression<Func<TView, TControl>> controlName,
diff --git a/src/ReactiveUI/Bindings/Command/ICommandBinderImplementation.cs b/src/ReactiveUI/Bindings/Command/ICommandBinderImplementation.cs
index e070a47f34..eb36d5ca7a 100644
--- a/src/ReactiveUI/Bindings/Command/ICommandBinderImplementation.cs
+++ b/src/ReactiveUI/Bindings/Command/ICommandBinderImplementation.cs
@@ -31,7 +31,7 @@ internal interface ICommandBinderImplementation : IEnableLogger
         /// <typeparam name="TParam">The type of the parameter to pass to the ICommand.</typeparam>
         /// <returns>A reactive binding. Often only used for disposing the binding.</returns>
         IReactiveBinding<TView, TProp> BindCommand<TView, TViewModel, TProp, TControl, TParam>(
-                TViewModel viewModel,
+                TViewModel? viewModel,
                 TView view,
                 Expression<Func<TViewModel, TProp>> propertyName,
                 Expression<Func<TView, TControl>> controlName,
@@ -57,7 +57,7 @@ IReactiveBinding<TView, TProp> BindCommand<TView, TViewModel, TProp, TControl, T
         /// <typeparam name="TParam">The type of the parameter to pass to the ICommand.</typeparam>
         /// <returns>A reactive binding. Often only used for disposing the binding.</returns>
         IReactiveBinding<TView, TProp> BindCommand<TView, TViewModel, TProp, TControl, TParam>(
-                TViewModel viewModel,
+                TViewModel? viewModel,
                 TView view,
                 Expression<Func<TViewModel, TProp>> propertyName,
                 Expression<Func<TView, TControl>> controlName,