diff --git a/mps/code/cbs.c b/mps/code/cbs.c
index 1835d2dee07..7e221a6b3f8 100644
--- a/mps/code/cbs.c
+++ b/mps/code/cbs.c
@@ -165,9 +165,9 @@ static void cbsUpdateNode(SplayTree tree, Tree node)
   Size maxSize;
   CBSBlock block;
 
-  AVERT(SplayTree, tree);
-  AVERT(Tree, node);
-  AVER(cbsOfTree(tree)->fastFind);
+  AVERT_CRITICAL(SplayTree, tree);
+  AVERT_CRITICAL(Tree, node);
+  AVER_CRITICAL(cbsOfTree(tree)->fastFind);
 
   block = cbsBlockOfNode(node);
   maxSize = CBSBlockSize(block);