diff --git a/doc/config.md b/doc/config.md
index e8a9d8626..526ebbf20 100644
--- a/doc/config.md
+++ b/doc/config.md
@@ -31,7 +31,7 @@ Defaults to 1. This is a default option that should not be changed or things wil
 
 ## zindex=1
 
-Defaults to 0. This option enables the "shielded index" which also calculates the "anonset" (anonymity set) also known as the "shielded pool". This data is avaailable in the getchaintxstats RPC, if zindex is enabled.
+Defaults to 0. This option enables the "shielded index" which also calculates the "anonset" (anonymity set) also known as the "shielded pool". This data is avaailable in the getchaintxstats RPC, if zindex is enabled. Enabling this feature requires a full rescan or full sync from scratch, which is not done by default. If you don't do one of those things, your zindex stats will be incorrect.
 
 # Mining options