diff --git a/syntax/elm.vim b/syntax/elm.vim
index be23595..be70e23 100644
--- a/syntax/elm.vim
+++ b/syntax/elm.vim
@@ -5,7 +5,7 @@ if exists('b:current_syntax')
 endif
 
 " Keywords
-syn keyword elmConditional else if of then
+syn keyword elmConditional else if of then not
 syn keyword elmAlias alias
 syn keyword elmTypedef contained type port
 syn keyword elmImport exposing as import module where