Update runtime files
diff --git a/runtime/syntax/m4.vim b/runtime/syntax/m4.vim
index 6f229ea..366f658 100644
--- a/runtime/syntax/m4.vim
+++ b/runtime/syntax/m4.vim
@@ -21,6 +21,7 @@
syn match m4Variable contained "\$\d\+"
syn match m4Special contained "$[@*#]"
syn match m4Comment "\<\(m4_\)\=dnl\>.*" contains=SpellErrors
+syn match m4Comment "#.*" contains=SpellErrors
syn match m4Constants "\<\(m4_\)\=__file__"
syn match m4Constants "\<\(m4_\)\=__line__"
syn keyword m4Constants divnum sysval m4_divnum m4_sysval
@@ -32,7 +33,7 @@
syn keyword m4Statement divert undivert
syn region m4Command matchgroup=m4Type start="\<\(m4_\)\=\(undefine\|popdef\)("he=e-1 end=")" contains=@m4Top
syn region m4Function matchgroup=m4Type start="\<[_A-Z][_A-Z0-9]*("he=e-1 end=")" contains=@m4Top
-syn region m4String start="`" end="'" contained contains=@m4Top,@m4StringContents,SpellErrors
+syn region m4String start="`" end="'" contains=SpellErrors
syn cluster m4Top contains=m4Comment,m4Constants,m4Special,m4Variable,m4String,m4Paren,m4Command,m4Statement,m4Function
" Define the default highlighting.