diff --git a/misc/factor.vim.fgen b/misc/factor.vim.fgen
index 2db6ffa764..21bab78e86 100644
--- a/misc/factor.vim.fgen
+++ b/misc/factor.vim.fgen
@@ -12,7 +12,7 @@ IN: factor.vim.fgen
 " Vim syntax file
 " Language: Factor
 " Maintainer: Alex Chapman <chapman.alex@gmail.com>
-" Last Change: 2011 Mar 16
+" Last Change: 2011 Mar 17
 " To run: USING: html.templates html.templates.fhtml ; "resource:misc/factor.vim.fgen" <fhtml> call-template
 
 " For version 5.x: Clear all syntax items
@@ -58,8 +58,8 @@ syn keyword factorBoolean f t
 syn keyword factorBreakpoint B
 syn keyword factorFrySpecifier @ _ contained
 syn keyword factorDeclaration delimiter deprecated final flushable foldable inline recursive
-syn match factorCallQuotation /\<call(\s.*\s--\s.*\s)\>/
-syn match factorExecute /\<execute(\s.*\s--\s.*\s)\>/
+syn match factorCallQuotation /\<call(\s\(.*\s\)\?--\(\s.*\)\?\s)\>/
+syn match factorExecute /\<execute(\s\(.*\s\)\?--\(\s.*\)\?\s)\>/
 syn keyword factorCallNextMethod call-next-method
 
 <%
@@ -157,8 +157,8 @@ syn match factorMultiStringContents /.*/ contained
 "syn match factorStackEffectErr /\<)\>/
 "syn region factorStackEffectErr start=/\<(\>/ end=/\<)\>/
 "syn region factorStackEffect start=/\<(\>/ end=/\<)\>/ contained
-syn match factorStackEffect /\<(\s.*\s--\s.*\s)\>/ contained
-syn match factorLiteralStackEffect /\<((\s.*\s--\s.*\s))\>/
+syn match factorStackEffect /\<(\s\(.*\s\)\?--\(\s.*\)\?\s)\>/ contained
+syn match factorLiteralStackEffect /\<((\s\(.*\s\)\?--\(\s.*\)\?\s))\>/
 
 "adapted from lisp.vim
 if exists("g:factor_norainbow")
diff --git a/misc/vim/syntax/factor.vim b/misc/vim/syntax/factor.vim
index 62004df82d..19d8cd2f40 100644
--- a/misc/vim/syntax/factor.vim
+++ b/misc/vim/syntax/factor.vim
@@ -1,7 +1,7 @@
 " Vim syntax file
 " Language: Factor
 " Maintainer: Alex Chapman <chapman.alex@gmail.com>
-" Last Change: 2011 Mar 16
+" Last Change: 2011 Mar 17
 " To run: USING: html.templates html.templates.fhtml ; "resource:misc/factor.vim.fgen" <fhtml> call-template
 
 " For version 5.x: Clear all syntax items
@@ -47,8 +47,8 @@ syn keyword factorBoolean f t
 syn keyword factorBreakpoint B
 syn keyword factorFrySpecifier @ _ contained
 syn keyword factorDeclaration delimiter deprecated final flushable foldable inline recursive
-syn match factorCallQuotation /\<call(\s.*\s--\s.*\s)\>/
-syn match factorExecute /\<execute(\s.*\s--\s.*\s)\>/
+syn match factorCallQuotation /\<call(\s\(.*\s\)\?--\(\s.*\)\?\s)\>/
+syn match factorExecute /\<execute(\s\(.*\s\)\?--\(\s.*\)\?\s)\>/
 syn keyword factorCallNextMethod call-next-method
 
 syn keyword factorKeyword or 2bi 2tri while wrapper nip 4dip wrapper? bi* callstack>array both? hashcode die dupd callstack callstack? 3dup tri@ pick curry build ?execute 3bi prepose >boolean ?if clone eq? tri* ? = swapd 2over 2keep 3keep clear 2dup when not tuple? dup 2bi* 2tri* call tri-curry object bi@ do unless* if* loop bi-curry* drop when* assert= retainstack assert? -rot execute 2bi@ 2tri@ boa with either? 3drop bi curry? datastack until 3dip over 3curry tri-curry* tri-curry@ swap and 2nip throw bi-curry (clone) hashcode* compose 2dip if 3tri unless compose? tuple keep 2curry equal? assert tri 2drop most <wrapper> boolean? identity-hashcode identity-tuple? null new dip bi-curry@ rot xor identity-tuple boolean
@@ -144,8 +144,8 @@ syn match factorMultiStringContents /.*/ contained
 "syn match factorStackEffectErr /\<)\>/
 "syn region factorStackEffectErr start=/\<(\>/ end=/\<)\>/
 "syn region factorStackEffect start=/\<(\>/ end=/\<)\>/ contained
-syn match factorStackEffect /\<(\s.*\s--\s.*\s)\>/ contained
-syn match factorLiteralStackEffect /\<((\s.*\s--\s.*\s))\>/
+syn match factorStackEffect /\<(\s\(.*\s\)\?--\(\s.*\)\?\s)\>/ contained
+syn match factorLiteralStackEffect /\<((\s\(.*\s\)\?--\(\s.*\)\?\s))\>/
 
 "adapted from lisp.vim
 if exists("g:factor_norainbow")