diff --git a/runtime/syntax/c.vim b/runtime/syntax/c.vim
index 7925e88..d07aaf2 100644
--- a/runtime/syntax/c.vim
+++ b/runtime/syntax/c.vim
@@ -1,7 +1,7 @@
 " Vim syntax file
 " Language:	C
 " Maintainer:	Bram Moolenaar <Bram@vim.org>
-" Last Change:	2020 Aug 28
+" Last Change:	2021 Jan 11
 
 " Quit when a (custom) syntax file was already loaded
 if exists("b:current_syntax")
@@ -13,6 +13,9 @@
 
 let s:ft = matchstr(&ft, '^\([^.]\)\+')
 
+" check if this was included from cpp.vim
+let s:in_cpp_family = exists("b:filetype_in_cpp_family")
+
 " Optional embedded Autodoc parsing
 " To enable it add: let g:c_autodoc = 1
 " to your .vimrc
@@ -55,7 +58,7 @@
 endif
 
 " cCppString: same as cString, but ends at end of line
-if s:ft ==# "cpp" && !exists("cpp_no_cpp11") && !exists("c_no_cformat")
+if s:in_cpp_family && !exists("cpp_no_cpp11") && !exists("c_no_cformat")
   " ISO C++11
   syn region	cString		start=+\(L\|u\|u8\|U\|R\|LR\|u8R\|uR\|UR\)\="+ skip=+\\\\\|\\"+ end=+"+ contains=cSpecial,cFormat,@Spell extend
   syn region 	cCppString	start=+\(L\|u\|u8\|U\|R\|LR\|u8R\|uR\|UR\)\="+ skip=+\\\\\|\\"\|\\$+ excludenl end=+"+ end='$' contains=cSpecial,cFormat,@Spell
@@ -87,7 +90,7 @@
 syn match	cSpecialCharacter display "'\\x\x\{1,2}'"
 syn match	cSpecialCharacter display "L'\\x\x\+'"
 
-if (s:ft ==# "c" && !exists("c_no_c11")) || (s:ft ==# "cpp" && !exists("cpp_no_cpp11"))
+if (s:ft ==# "c" && !exists("c_no_c11")) || (s:in_cpp_family && !exists("cpp_no_cpp11"))
   " ISO C11 or ISO C++ 11
   if exists("c_no_cformat")
     syn region	cString		start=+\%(U\|u8\=\)"+ skip=+\\\\\|\\"+ end=+"+ contains=cSpecial,@Spell extend
@@ -130,7 +133,7 @@
 " But avoid matching <::.
 syn cluster	cParenGroup	contains=cParenError,cIncluded,cSpecial,cCommentSkip,cCommentString,cComment2String,@cCommentGroup,cCommentStartError,cUserLabel,cBitField,cOctalZero,@cCppOutInGroup,cFormat,cNumber,cFloat,cOctal,cOctalError,cNumbersCom
 if exists("c_no_curly_error")
-  if s:ft ==# 'cpp' && !exists("cpp_no_cpp11")
+  if s:in_cpp_family && !exists("cpp_no_cpp11")
     syn region	cParen		transparent start='(' end=')' contains=ALLBUT,@cParenGroup,cCppParen,@cStringGroup,@Spell
     " cCppParen: same as cParen but ends at end-of-line; used in cDefine
     syn region	cCppParen	transparent start='(' skip='\\$' excludenl end=')' end='$' contained contains=ALLBUT,@cParenGroup,cParen,cString,@Spell
@@ -144,7 +147,7 @@
     syn match	cErrInParen	display contained "^[{}]\|^<%\|^%>"
   endif
 elseif exists("c_no_bracket_error")
-  if s:ft ==# 'cpp' && !exists("cpp_no_cpp11")
+  if s:in_cpp_family && !exists("cpp_no_cpp11")
     syn region	cParen		transparent start='(' end=')' contains=ALLBUT,@cParenGroup,cCppParen,@cStringGroup,@Spell
     " cCppParen: same as cParen but ends at end-of-line; used in cDefine
     syn region	cCppParen	transparent start='(' skip='\\$' excludenl end=')' end='$' contained contains=ALLBUT,@cParenGroup,cParen,cString,@Spell
@@ -158,7 +161,7 @@
     syn match	cErrInParen	display contained "[{}]\|<%\|%>"
   endif
 else
-  if s:ft ==# 'cpp' && !exists("cpp_no_cpp11")
+  if s:in_cpp_family && !exists("cpp_no_cpp11")
     syn region	cParen		transparent start='(' end=')' contains=ALLBUT,@cParenGroup,cCppParen,cErrInBracket,cCppBracket,@cStringGroup,@Spell
     " cCppParen: same as cParen but ends at end-of-line; used in cDefine
     syn region	cCppParen	transparent start='(' skip='\\$' excludenl end=')' end='$' contained contains=ALLBUT,@cParenGroup,cErrInBracket,cParen,cBracket,cString,@Spell
@@ -278,7 +281,7 @@
 if exists("c_gnu")
   syn keyword	cStorageClass	inline __attribute__
 endif
-if !exists("c_no_c99") && s:ft !=# 'cpp'
+if !exists("c_no_c99") && !s:in_cpp_family
   syn keyword	cStorageClass	inline restrict
 endif
 if !exists("c_no_c11")
@@ -420,7 +423,7 @@
 syn cluster	cLabelGroup	contains=cUserLabel
 syn match	cUserCont	display "^\s*\zs\I\i*\s*:$" contains=@cLabelGroup
 syn match	cUserCont	display ";\s*\zs\I\i*\s*:$" contains=@cLabelGroup
-if s:ft ==# 'cpp'
+if s:in_cpp_family
   syn match	cUserCont	display "^\s*\zs\%(class\|struct\|enum\)\@!\I\i*\s*:[^:]"me=e-1 contains=@cLabelGroup
   syn match	cUserCont	display ";\s*\zs\%(class\|struct\|enum\)\@!\I\i*\s*:[^:]"me=e-1 contains=@cLabelGroup
 else
diff --git a/runtime/syntax/cpp.vim b/runtime/syntax/cpp.vim
index 53b6a51..ed38913 100644
--- a/runtime/syntax/cpp.vim
+++ b/runtime/syntax/cpp.vim
@@ -2,13 +2,16 @@
 " Language:	C++
 " Current Maintainer:	vim-jp (https://github.com/vim-jp/vim-cpp)
 " Previous Maintainer:	Ken Shan <ccshan@post.harvard.edu>
-" Last Change:	2019 Dec 18
+" Last Change:	2021 Jan 12
 
 " quit when a syntax file was already loaded
 if exists("b:current_syntax")
   finish
 endif
 
+" inform C syntax that the file was included from cpp.vim
+let b:filetype_in_cpp_family = 1
+
 " Read the C syntax to start with
 runtime! syntax/c.vim
 unlet b:current_syntax