diff --git a/docs/ApiValidationRules.md b/docs/ApiValidationRules.md
index 8a38a91..1e41b4f 100644
--- a/docs/ApiValidationRules.md
+++ b/docs/ApiValidationRules.md
@@ -189,6 +189,7 @@ shipcall_id, participant_id, participant_type
 
 1. A dataset may only be changed by a user belonging to the same participant as the times dataset is referring to.
 2. See reference and value checking as specified in /times POST.
+3. The shipcall type may not be changed. 
 
 #### Required fields