diff --git i/resources/data/validator/ignoretags.cfg w/resources/data/validator/ignoretags.cfg
index 41e0f3875d..0400666b0a 100644
--- i/resources/data/validator/ignoretags.cfg
+++ w/resources/data/validator/ignoretags.cfg
@@ -302,6 +302,7 @@ K:historic=farm
 ;
 K:landcover=grass
 K:landcover=trees
+K:landcover=mostly_rock
 ;
 ; Lifecycle Tags
 ;