diff --git a/src/Build/Collections/CopyOnReadEnumerable.cs b/src/Build/Collections/CopyOnReadEnumerable.cs
index 056f5804cfd..72da4089325 100644
--- a/src/Build/Collections/CopyOnReadEnumerable.cs
+++ b/src/Build/Collections/CopyOnReadEnumerable.cs
@@ -72,6 +72,10 @@ public IEnumerator<TResult> GetEnumerator()
 #endif
                 list = new List<TResult>(count);
             }
+            else if (_backingEnumerable is IReadOnlyCollection<TSource> readOnlyCollection)
+            {
+                list = new List<TResult>(readOnlyCollection.Count);
+            }
             else
             {
                 list = new List<TResult>();