diff --git a/CodeWalker.Core/GameFiles/FileTypes/YmapFile.cs b/CodeWalker.Core/GameFiles/FileTypes/YmapFile.cs
index 7eb1c56..67c7720 100644
--- a/CodeWalker.Core/GameFiles/FileTypes/YmapFile.cs
+++ b/CodeWalker.Core/GameFiles/FileTypes/YmapFile.cs
@@ -1050,6 +1050,10 @@ namespace CodeWalker.GameFiles
             {
                 contentFlags = SetBit(contentFlags, 6); //64
             }
+            if ((GrassInstanceBatches != null) && (GrassInstanceBatches.Length > 0))
+            {
+                contentFlags = SetBit(contentFlags, 10); //64
+            }
 
 
             bool change = false;