diff --git a/syntax/ats.vim b/syntax/ats.vim
index 6ee3c5c..0cb2159 100644
--- a/syntax/ats.vim
+++ b/syntax/ats.vim
@@ -37,7 +37,7 @@ syn match atsArrow '=/=>>'
 syn region atsArrow start="=<" end=">" contains=arrowContents
 syn region atsArrow start="-<" end=">"
 
-syn keyword atsType void bool string char int uint uint8 uint32 uint16 int8 int32 int16 charNZ strnptr Strptr0 Strptr1 nat lint ulint double float size_t llint ullint
+syn keyword atsType void bool string char int uint uint8 uint32 uint64 uint16 int8 int32 int16 int64 charNZ strnptr Strptr0 Strptr1 nat lint ulint double float size_t llint ullint
 syn keyword atsType datavtype datatype vtypedef dataviewtype viewtypdef typedef view viewdef dataview abstype absvtype absviewtype absview datasort dataprop type viewtype vtype propdef prop
 syn keyword atsType absimpl absprop
 syn keyword atsType implement primplmnt extern