diff --git a/doc/internals/hashing.mdwn b/doc/internals/hashing.mdwn
index bdc259b634..9895cad0e9 100644
--- a/doc/internals/hashing.mdwn
+++ b/doc/internals/hashing.mdwn
@@ -19,7 +19,8 @@ below is only for completeness.
 
 This uses two directories, each with a three-letter name, such as "f87/4d5"
 
-The directory names come from the md5sum of the [[key|key_format]].
+The directory names come from the first 6 characters of the md5sum of the [[key|key_format]]
+when serialized as a hex string.
 
 For example: