1 files changed, 10 insertions, 1 deletions
diff --git a/src/System.Private.CoreLib/shared/System/Collections/Generic/ValueListBuilder.cs b/src/System.Private.CoreLib/shared/System/Collections/Generic/ValueListBuilder.cs
index 72da4a9e1..aea6052f0 100644
--- a/src/System.Private.CoreLib/shared/System/Collections/Generic/ValueListBuilder.cs
+++ b/src/System.Private.CoreLib/shared/System/Collections/Generic/ValueListBuilder.cs
@@ -21,7 +21,16 @@ namespace System.Collections.Generic
             _pos = 0;
         }
 
-        public int Length => _pos;
+        public int Length
+        {
+            get => _pos;
+            set
+            {
+                Debug.Assert(value >= 0);
+                Debug.Assert(value <= _span.Length);
+                _pos = value;
+            }
+        }
 
         public ref T this[int index]
         {