diff --git a/syntax/reason.vim b/syntax/reason.vim
index ad5dddf..708e3a2 100644
--- a/syntax/reason.vim
+++ b/syntax/reason.vim
@@ -23,7 +23,7 @@ syn keyword   rustKeyword     box nextgroup=rustBoxPlacement skipwhite skipempty
 syn keyword   rustKeyword     extern nextgroup=rustExternCrate,rustObsoleteExternMod skipwhite skipempty
 " syn keyword   rustKeyword     fun nextgroup=rustFuncName skipwhite skipempty
 syn keyword   rustKeyword     unsafe where while lazy
-syn keyword   rustStorage     and class constraint exception external include inherit let method module nonrec open private rec type val with
+syn keyword   rustStorage     and class constraint exception external include inherit let method module nonrec open private rec type val with mutable
 " FIXME: Scoped impl's name is also fallen in this category
 " syn keyword   rustStorageIdent   let and module type nextgroup=rustIdentifier skipwhite skipempty