diff --git a/src/SimpleInjector.Integration.Web.Mvc/SimpleInjectorDependencyResolver.cs b/src/SimpleInjector.Integration.Web.Mvc/SimpleInjectorDependencyResolver.cs
index 1f380995f..c741787a3 100644
--- a/src/SimpleInjector.Integration.Web.Mvc/SimpleInjectorDependencyResolver.cs
+++ b/src/SimpleInjector.Integration.Web.Mvc/SimpleInjectorDependencyResolver.cs
@@ -114,6 +114,8 @@ public IEnumerable<object> GetServices(Type serviceType)
 
             var services = (IEnumerable<object>)this.ServiceProvider.GetService(collectionType);
 
+            // NOTE: The contract of IDependencyResolver isn't very clear, but MVC will break when null
+            // is returned.
             return services ?? Enumerable.Empty<object>();
         }
     }
diff --git a/src/SimpleInjector.Integration.WebApi/SimpleInjectorWebApiDependencyResolver.cs b/src/SimpleInjector.Integration.WebApi/SimpleInjectorWebApiDependencyResolver.cs
index f9885ee34..8b90c9ee9 100644
--- a/src/SimpleInjector.Integration.WebApi/SimpleInjectorWebApiDependencyResolver.cs
+++ b/src/SimpleInjector.Integration.WebApi/SimpleInjectorWebApiDependencyResolver.cs
@@ -185,6 +185,8 @@ IEnumerable<object> IDependencyScope.GetServices(Type serviceType)
 
             var services = (IEnumerable<object>)this.ServiceProvider.GetService(collectionType);
 
+            // NOTE: The contract of IDependencyScope isn't very clear, but Web API will break when null
+            // is returned.
             return services ?? Enumerable.Empty<object>();
         }