diff --git a/runtime/syntax/prolog.vim b/runtime/syntax/prolog.vim
index f5f0e67..2131308 100644
--- a/runtime/syntax/prolog.vim
+++ b/runtime/syntax/prolog.vim
@@ -8,10 +8,8 @@
 " If the "prolog_highlighting_clean" variable exists, it is rather sparse.
 " Otherwise you get more highlighting.
 
-" Quit when a syntax file was already loaded
-if version < 600
-   syntax clear
-elseif exists("b:current_syntax")
+" quit when a syntax file was already loaded
+if exists("b:current_syntax")
   finish
 endif
 
@@ -78,46 +76,38 @@
 
 
 " Define the default highlighting.
-" For version 5.7 and earlier: only when not done already
-" For version 5.8 and later: only when an item doesn't have highlighting yet
-if version >= 508 || !exists("did_prolog_syn_inits")
-  if version < 508
-    let did_prolog_syn_inits = 1
-    command -nargs=+ HiLink hi link <args>
-  else
-    command -nargs=+ HiLink hi def link <args>
-  endif
+" Only when an item doesn't have highlighting yet
+command -nargs=+ HiLink hi def link <args>
 
-  " The default highlighting.
-  HiLink prologComment          Comment
-  HiLink prologCComment         Comment
-  HiLink prologCharCode         Special
+" The default highlighting.
+HiLink prologComment          Comment
+HiLink prologCComment         Comment
+HiLink prologCharCode         Special
 
-  if exists ("prolog_highlighting_clean")
+if exists ("prolog_highlighting_clean")
 
-    HiLink prologKeyword        Statement
-    HiLink prologClauseHead     Statement
-    HiLink prologClause Normal
+HiLink prologKeyword        Statement
+HiLink prologClauseHead     Statement
+HiLink prologClause Normal
 
-  else
+else
 
-    HiLink prologKeyword        Keyword
-    HiLink prologClauseHead     Constant
-    HiLink prologClause Normal
-    HiLink prologQuestion       PreProc
-    HiLink prologSpecialCharacter Special
-    HiLink prologNumber         Number
-    HiLink prologAsIs           Normal
-    HiLink prologCommentError   Error
-    HiLink prologAtom           String
-    HiLink prologString         String
-    HiLink prologOperator       Operator
+HiLink prologKeyword        Keyword
+HiLink prologClauseHead     Constant
+HiLink prologClause Normal
+HiLink prologQuestion       PreProc
+HiLink prologSpecialCharacter Special
+HiLink prologNumber         Number
+HiLink prologAsIs           Normal
+HiLink prologCommentError   Error
+HiLink prologAtom           String
+HiLink prologString         String
+HiLink prologOperator       Operator
 
-  endif
-
-  delcommand HiLink
 endif
 
+delcommand HiLink
+
 let b:current_syntax = "prolog"
 
 " vim: ts=8