diff --git a/core/java/src/net/i2p/data/Hash.java b/core/java/src/net/i2p/data/Hash.java
index 627f02c396bb16b05763cb2787c79aeb210e9256..23d466d6854e34db37b02151099f2583e664d9fd 100644
--- a/core/java/src/net/i2p/data/Hash.java
+++ b/core/java/src/net/i2p/data/Hash.java
@@ -30,6 +30,14 @@ public class Hash extends SimpleDataStructure {
 
     /**
      * Pull from cache or return new
+     *
+     *  WARNING - If the SDS is found in the cache, the passed-in
+     *  byte array will be returned to the SimpleByteCache for reuse.
+     *  Do NOT save a reference to the passed-in data, or use or modify it,
+     *  after this call.
+     *
+     *  Ignore this warning and you WILL corrupt the cache or other data structures.
+     *
      * @throws IllegalArgumentException if data is not the correct number of bytes
      * @since 0.8.3
      */