diff --git a/syntax/reason.vim b/syntax/reason.vim
index e19b0a3..086da25 100644
--- a/syntax/reason.vim
+++ b/syntax/reason.vim
@@ -14,7 +14,7 @@ endif
 
 " Syntax definitions {{{1
 " Basic keywords {{{2
-syn keyword   rustConditional switch match if else for in
+syn keyword   rustConditional switch match if else for in when fun
 syn keyword   rustOperator    as
 
 syn match     rustAssert      "\<assert\(\w\)*!" contained