diff --git a/Runtime/Observable/ObservableList.cs b/Runtime/Observable/ObservableList.cs
index c67034b..f411f22 100644
--- a/Runtime/Observable/ObservableList.cs
+++ b/Runtime/Observable/ObservableList.cs
@@ -168,6 +168,7 @@ public void RemoveAt(int index)
 
         public void RemoveRange(int startIndex, int count)
         {
+            if (startIndex < 0) throw new ArgumentOutOfRangeException(nameof(startIndex));
             if (count < 0) throw new ArgumentOutOfRangeException(nameof(count));
 
             lock (SyncRoot)