diff --git a/src/Umbraco.Core/Components/CompositionExtensions.cs b/src/Umbraco.Core/Components/CompositionExtensions.cs
index a4bc82cb4b..bb23e89b81 100644
--- a/src/Umbraco.Core/Components/CompositionExtensions.cs
+++ b/src/Umbraco.Core/Components/CompositionExtensions.cs
@@ -281,6 +281,22 @@ namespace Umbraco.Core.Components
             composition.RegisterUnique(_ => helper);
         }
 
+        /// <summary>
+        /// Sets the underlying media filesystem.
+        /// </summary>
+        /// <param name="composition">A composition.</param>
+        /// <param name="filesystemFactory">A filesystem factory.</param>
+        public static void SetMediaFileSystem(this Composition composition, Func<IFactory, IFileSystem> filesystemFactory)
+            => composition.RegisterUniqueFor<IFileSystem, IMediaFileSystem>(filesystemFactory);
+
+        /// <summary>
+        /// Sets the underlying media filesystem.
+        /// </summary>
+        /// <param name="composition">A composition.</param>
+        /// <param name="filesystemFactory">A filesystem factory.</param>
+        public static void SetMediaFileSystem(this Composition composition, Func<IFileSystem> filesystemFactory)
+            => composition.RegisterUniqueFor<IFileSystem, IMediaFileSystem>(_ => filesystemFactory());
+
         #endregion
     }
 }
diff --git a/src/Umbraco.Core/Composing/Composers/FileSystemsComposer.cs b/src/Umbraco.Core/Composing/Composers/FileSystemsComposer.cs
index ab4bd015de..4c598f27e4 100644
--- a/src/Umbraco.Core/Composing/Composers/FileSystemsComposer.cs
+++ b/src/Umbraco.Core/Composing/Composers/FileSystemsComposer.cs
@@ -88,9 +88,9 @@ namespace Umbraco.Core.Composing.Composers
             composition.Register(factory => new SupportingFileSystems(factory), Lifetime.Singleton);
 
             // register the IFileSystem supporting the IMediaFileSystem
-            // this is the only thing that need to be overriden to change the supporting filesystem
+            // THIS IS THE ONLY THING THAT NEEDS TO CHANGE, IN ORDER TO REPLACE THE UNDERLYING FILESYSTEM
             // and, SupportingFileSystem.For<IMediaFileSystem>() returns the underlying filesystem
-            composition.RegisterUniqueFor<IFileSystem, IMediaFileSystem>(_ => new PhysicalFileSystem("~/media"));
+            composition.SetMediaFileSystem(() => new PhysicalFileSystem("~/media"));
 
             return composition;
         }
diff --git a/src/Umbraco.Core/Composing/IRegister.cs b/src/Umbraco.Core/Composing/IRegister.cs
index 3e6aed67ee..cbf12f54a3 100644
--- a/src/Umbraco.Core/Composing/IRegister.cs
+++ b/src/Umbraco.Core/Composing/IRegister.cs
@@ -36,24 +36,40 @@ namespace Umbraco.Core.Composing
         /// <summary>
         /// Registers a service for a target, as its own implementation.
         /// </summary>
+        /// <remarks>
+        /// There can only be one implementation or instanced registered for a service and target;
+        /// what happens if many are registered is not specified.
+        /// </remarks>
         void RegisterFor<TService, TTarget>(Lifetime lifetime = Lifetime.Transient)
             where TService : class;
 
         /// <summary>
         /// Registers a service for a target, with an implementation type.
         /// </summary>
+        /// <remarks>
+        /// There can only be one implementation or instanced registered for a service and target;
+        /// what happens if many are registered is not specified.
+        /// </remarks>
         void RegisterFor<TService, TTarget>(Type implementingType, Lifetime lifetime = Lifetime.Transient)
             where TService : class;
 
         /// <summary>
         /// Registers a service for a target, with an implementation factory.
         /// </summary>
+        /// <remarks>
+        /// There can only be one implementation or instanced registered for a service and target;
+        /// what happens if many are registered is not specified.
+        /// </remarks>
         void RegisterFor<TService, TTarget>(Func<IFactory, TService> factory, Lifetime lifetime = Lifetime.Transient)
             where TService : class;
 
         /// <summary>
         /// Registers a service for a target, with an implementing instance.
         /// </summary>
+        /// <remarks>
+        /// There can only be one implementation or instanced registered for a service and target;
+        /// what happens if many are registered is not specified.
+        /// </remarks>
         void RegisterFor<TService, TTarget>(TService instance)
             where TService : class;