diff --git a/hbase-oss/README.md b/hbase-oss/README.md
index ec433d9..4755143 100644
--- a/hbase-oss/README.md
+++ b/hbase-oss/README.md
@@ -43,6 +43,10 @@
 The null implementation just provides no-op methods instead of actual locking
 operations. This functions as an easy way to verify that a test case has
 successfully reproduced a problem that is hidden by the other implementations.
+Notice this implementation should consistently fail tests enforcing atomicity,
+such as TestAtomicRename and TestCreateNonRecursive. Additional tests may
+eventually fail due to unpredictable race conditions, since no lock behaviour
+is being implemented.
 
 ### Local Implementation (org.apache.hadoop.hbase.oss.sync.LocalTreeLockManager)