diff --git a/src/libraries/System.Collections.Immutable/src/System/Collections/Immutable/ImmutableList_1.Node.cs b/src/libraries/System.Collections.Immutable/src/System/Collections/Immutable/ImmutableList_1.Node.cs
index ef0381384f29ac..ac8efc506b439a 100644
--- a/src/libraries/System.Collections.Immutable/src/System/Collections/Immutable/ImmutableList_1.Node.cs
+++ b/src/libraries/System.Collections.Immutable/src/System/Collections/Immutable/ImmutableList_1.Node.cs
@@ -196,15 +196,20 @@ internal ref readonly T ItemRef(int index)
             {
                 Requires.Range(index >= 0 && index < this.Count, nameof(index));
 
+                return ref ItemRefUnchecked(index);
+            }
+
+            private ref readonly T ItemRefUnchecked(int index)
+            {
                 Debug.Assert(_left != null && _right != null);
                 if (index < _left._count)
                 {
-                    return ref _left.ItemRef(index);
+                    return ref _left.ItemRefUnchecked(index);
                 }
 
                 if (index > _left._count)
                 {
-                    return ref _right.ItemRef(index - _left._count - 1);
+                    return ref _right.ItemRefUnchecked(index - _left._count - 1);
                 }
 
                 return ref _key;
diff --git a/src/libraries/System.Collections.Immutable/src/System/Collections/Immutable/ImmutableSortedSet_1.Node.cs b/src/libraries/System.Collections.Immutable/src/System/Collections/Immutable/ImmutableSortedSet_1.Node.cs
index 89b044c0ce9793..44d7f1768c6785 100644
--- a/src/libraries/System.Collections.Immutable/src/System/Collections/Immutable/ImmutableSortedSet_1.Node.cs
+++ b/src/libraries/System.Collections.Immutable/src/System/Collections/Immutable/ImmutableSortedSet_1.Node.cs
@@ -261,16 +261,22 @@ internal T this[int index]
             internal ref readonly T ItemRef(int index)
             {
                 Requires.Range(index >= 0 && index < this.Count, nameof(index));
+
+                return ref ItemRefUnchecked(index);
+            }
+
+            private ref readonly T ItemRefUnchecked(int index)
+            {
                 Debug.Assert(_left != null && _right != null);
 
                 if (index < _left._count)
                 {
-                    return ref _left.ItemRef(index);
+                    return ref _left.ItemRefUnchecked(index);
                 }
 
                 if (index > _left._count)
                 {
-                    return ref _right.ItemRef(index - _left._count - 1);
+                    return ref _right.ItemRefUnchecked(index - _left._count - 1);
                 }
 
                 return ref _key;