diff --git a/sync/optimistic.md b/sync/optimistic.md
index 553c3e487..c1841d2dd 100644
--- a/sync/optimistic.md
+++ b/sync/optimistic.md
@@ -108,6 +108,7 @@ When an execution engine returns an error or fails to respond to a payload
 validity request some block, a consensus engine:
 
 - MUST NOT optimistically import the block.
+- MUST NOT apply the block to the fork choice store.
 - MAY queue the block for later processing.
 
 ### Assumptions about Execution Engine Behaviour