diff --git a/src/Compilers/Core/Portable/InternalUtilities/SetWithInsertionOrder.cs b/src/Compilers/Core/Portable/InternalUtilities/SetWithInsertionOrder.cs
index ea6f522113ebb45eb44202a22001011ead7f2c84..6f9ebf5ff533650d9dbc545819dca84d490ba906 100644
--- a/src/Compilers/Core/Portable/InternalUtilities/SetWithInsertionOrder.cs
+++ b/src/Compilers/Core/Portable/InternalUtilities/SetWithInsertionOrder.cs
@@ -96,7 +96,6 @@ public IEnumerator<T> GetEnumerator()
 
         public ImmutableArray<T> AsImmutable() => _elements.ToImmutableArrayOrEmpty();
 
-        [MaybeNull]
-        public T this[int i] => _elements is null ? default : _elements[i];
+        public T this[int i] => _elements![i];
     }
 }