diff --git a/syntax/ats.vim b/syntax/ats.vim
index 90ae9da..0cc9192 100644
--- a/syntax/ats.vim
+++ b/syntax/ats.vim
@@ -81,7 +81,7 @@ syn keyword atsExternal extern implement
 syn keyword atsKeyword symintr overload with
 syn keyword atsKeyword prval praxi datasort
 
-syn keyword atsSorts bool char int prop type view viewtype nat
+syn keyword atsSorts bool char int prop type view viewtype nat absvtype
 
 syn keyword atsTypes string float double void