diff --git a/src/Caliburn.Micro.Platform/AssemblySource.cs b/src/Caliburn.Micro.Platform/AssemblySource.cs
index 17021b7fe..3f67bd1cb 100644
--- a/src/Caliburn.Micro.Platform/AssemblySource.cs
+++ b/src/Caliburn.Micro.Platform/AssemblySource.cs
@@ -17,6 +17,27 @@ public static class AssemblySource
         /// </summary>
         public static readonly IObservableCollection<Assembly> Instance = new BindableCollection<Assembly>();
 
+
+        /// <summary>
+        /// Adds a collection of assemblies to AssemblySource
+        /// </summary>
+        /// <param name="assemblies">The assemblies to add</param>
+        public static void AddRange(IEnumerable<Assembly> assemblies)
+        {
+            foreach(var assembly in assemblies)
+            {
+                try
+                {
+                    if (!Instance.Contains(assembly))
+                        Instance.Add(assembly);
+                }
+                catch (ArgumentException)
+                {
+                    // ignore
+                }
+            }
+        }
+
         /// <summary>
         /// Finds a type which matches one of the elements in the sequence of names.
         /// </summary>
diff --git a/src/Caliburn.Micro.Platform/Platforms/Android/CaliburnApplication.cs b/src/Caliburn.Micro.Platform/Platforms/Android/CaliburnApplication.cs
index 3b80222ea..371de01a7 100644
--- a/src/Caliburn.Micro.Platform/Platforms/Android/CaliburnApplication.cs
+++ b/src/Caliburn.Micro.Platform/Platforms/Android/CaliburnApplication.cs
@@ -30,7 +30,7 @@ public CaliburnApplication(IntPtr javaReference, JniHandleOwnership transfer)
         protected virtual void StartDesignTime()
         {
             AssemblySource.Instance.Clear();
-            AssemblySource.Instance.AddRange(SelectAssemblies());
+            AssemblySource.AddRange(SelectAssemblies());
 
             Configure();
 
@@ -45,7 +45,7 @@ protected virtual void StartDesignTime()
         protected virtual void StartRuntime()
         {
             AssemblySourceCache.Install();
-            AssemblySource.Instance.AddRange(SelectAssemblies());
+            AssemblySource.AddRange(SelectAssemblies());
 
             Configure();
 
diff --git a/src/Caliburn.Micro.Platform/Platforms/iOS/CaliburnApplicationDelegate.cs b/src/Caliburn.Micro.Platform/Platforms/iOS/CaliburnApplicationDelegate.cs
index 412b60dda..64a5ad6cd 100644
--- a/src/Caliburn.Micro.Platform/Platforms/iOS/CaliburnApplicationDelegate.cs
+++ b/src/Caliburn.Micro.Platform/Platforms/iOS/CaliburnApplicationDelegate.cs
@@ -43,7 +43,7 @@ public CaliburnApplicationDelegate(NSObjectFlag t)
         protected virtual void StartDesignTime()
         {
             AssemblySource.Instance.Clear();
-            AssemblySource.Instance.AddRange(SelectAssemblies());
+            AssemblySource.AddRange(SelectAssemblies());
 
             Configure();
 
@@ -58,7 +58,7 @@ protected virtual void StartDesignTime()
         protected virtual void StartRuntime()
         {
             AssemblySourceCache.Install();
-            AssemblySource.Instance.AddRange(SelectAssemblies());
+            AssemblySource.AddRange(SelectAssemblies());
 
             Configure();
             IoC.GetInstance = GetInstance;
diff --git a/src/Caliburn.Micro.Platform/Platforms/net46-netcore/Bootstrapper.cs b/src/Caliburn.Micro.Platform/Platforms/net46-netcore/Bootstrapper.cs
index e53b444f5..820d18e4e 100644
--- a/src/Caliburn.Micro.Platform/Platforms/net46-netcore/Bootstrapper.cs
+++ b/src/Caliburn.Micro.Platform/Platforms/net46-netcore/Bootstrapper.cs
@@ -83,7 +83,7 @@ public void Initialize()
         protected virtual void StartDesignTime()
         {
             AssemblySource.Instance.Clear();
-            AssemblySource.Instance.AddRange(SelectAssemblies());
+            AssemblySource.AddRange(SelectAssemblies());
 
             Configure();
             IoC.GetInstance = GetInstance;
@@ -97,7 +97,7 @@ protected virtual void StartDesignTime()
         protected virtual void StartRuntime()
         {
             AssemblySourceCache.Install();
-            AssemblySource.Instance.AddRange(SelectAssemblies());
+            AssemblySource.AddRange(SelectAssemblies());
 
             if (useApplication)
             {
diff --git a/src/Caliburn.Micro.Platform/Platforms/net46/Bootstrapper.cs b/src/Caliburn.Micro.Platform/Platforms/net46/Bootstrapper.cs
index e53b444f5..820d18e4e 100644
--- a/src/Caliburn.Micro.Platform/Platforms/net46/Bootstrapper.cs
+++ b/src/Caliburn.Micro.Platform/Platforms/net46/Bootstrapper.cs
@@ -83,7 +83,7 @@ public void Initialize()
         protected virtual void StartDesignTime()
         {
             AssemblySource.Instance.Clear();
-            AssemblySource.Instance.AddRange(SelectAssemblies());
+            AssemblySource.AddRange(SelectAssemblies());
 
             Configure();
             IoC.GetInstance = GetInstance;
@@ -97,7 +97,7 @@ protected virtual void StartDesignTime()
         protected virtual void StartRuntime()
         {
             AssemblySourceCache.Install();
-            AssemblySource.Instance.AddRange(SelectAssemblies());
+            AssemblySource.AddRange(SelectAssemblies());
 
             if (useApplication)
             {
diff --git a/src/Caliburn.Micro.Platform/Platforms/uap/CaliburnApplication.cs b/src/Caliburn.Micro.Platform/Platforms/uap/CaliburnApplication.cs
index 2f9848142..34d0432b1 100644
--- a/src/Caliburn.Micro.Platform/Platforms/uap/CaliburnApplication.cs
+++ b/src/Caliburn.Micro.Platform/Platforms/uap/CaliburnApplication.cs
@@ -28,7 +28,7 @@ public abstract class CaliburnApplication : Application
         protected virtual void StartDesignTime()
         {
             AssemblySource.Instance.Clear();
-            AssemblySource.Instance.AddRange(SelectAssemblies());
+            AssemblySource.AddRange(SelectAssemblies());
 
             Configure();
             IoC.GetInstance = GetInstance;
@@ -42,7 +42,7 @@ protected virtual void StartDesignTime()
         protected virtual void StartRuntime()
         {
             AssemblySourceCache.Install();
-            AssemblySource.Instance.AddRange(SelectAssemblies());
+            AssemblySource.AddRange(SelectAssemblies());
 
             PrepareApplication();
             Configure();