diff --git a/contrib/vim/syntax/bitbake.vim b/contrib/vim/syntax/bitbake.vim
index a06dd9e..336e6bb 100644
--- a/contrib/vim/syntax/bitbake.vim
+++ b/contrib/vim/syntax/bitbake.vim
@@ -52,8 +52,8 @@ syn match bbExport            "^export" nextgroup=bbIdentifier skipwhite
 syn keyword bbExportFlag        export contained nextgroup=bbIdentifier skipwhite
 syn match bbIdentifier          "[a-zA-Z0-9\-_\.\/\+]\+" display contained
 syn match bbVarDeref            "${[a-zA-Z0-9\-_\.\/\+]\+}" contained
-syn match bbVarEq               "\(:=\|+=\|=+\|\.=\|=\.\|?=\|=\)" contained nextgroup=bbVarValue
-syn match bbVarDef              "^\(export\s*\)\?\([a-zA-Z0-9\-_\.\/\+]\+\(_[${}a-zA-Z0-9\-_\.\/\+]\+\)\?\)\s*\(:=\|+=\|=+\|\.=\|=\.\|?=\|=\)\@=" contains=bbExportFlag,bbIdentifier,bbVarDeref nextgroup=bbVarEq
+syn match bbVarEq               "\(:=\|+=\|=+\|\.=\|=\.\|?=\|??=\|=\)" contained nextgroup=bbVarValue
+syn match bbVarDef              "^\(export\s*\)\?\([a-zA-Z0-9\-_\.\/\+]\+\(_[${}a-zA-Z0-9\-_\.\/\+]\+\)\?\)\s*\(:=\|+=\|=+\|\.=\|=\.\|?=\|??=\|=\)\@=" contains=bbExportFlag,bbIdentifier,bbVarDeref nextgroup=bbVarEq
 syn match bbVarValue            ".*$" contained contains=bbString,bbVarDeref,bbVarPyValue
 syn region bbVarPyValue         start=+${@+ skip=+\\$+ excludenl end=+}+ contained contains=@python