diff --git a/ChangeLog b/ChangeLog
index 648852f146..c57261f43b 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,17 @@
+Tue Nov 13 15:26:33 2007  Tanaka Akira  <akr@fsij.org>
+
+	* lex.c.blt: moved from lex.c.
+
+	* lex.c.src: copied from keywords.  This is the source of lex.c.blt.
+
+	* Makefile.in (lex.c): use lex.c.blt if keywords is same as lex.c.src.
+
+	* win32/Makefile.sub (lex.c): re-introduce copy rule.
+
+	* bcc32/Makefile.sub (lex.c): ditto.
+
+	* wince/Makefile.sub (lex.c): ditto.
+
 Tue Nov 13 15:21:52 2007  Koichi Sasada  <ko1@atdot.net>
 
 	* compile.c (iseq_specialized_instruction): check argc.
diff --git a/Makefile.in b/Makefile.in
index 6a4720c940..5d9dcf36ef 100644
--- a/Makefile.in
+++ b/Makefile.in
@@ -168,11 +168,13 @@ $(srcdir)/configure: $(srcdir)/configure.in
 # * svn checkout generate a file with mtime as current time
 # * XFS has a mtime with fractional part
 lex.c: keywords
-	( gperf -C -p -j1 -i 1 -g -o -t -N rb_reserved_word -k1,3,$$ $? > $@.tmp && mv $@.tmp $@ ) || \
-	if test -f $@; then \
-	  touch $@ && echo $@ touched.; \
+	if cmp -s $(srcdir)/lex.c.src $?; then \
+	  cp $(srcdir)/lex.c.blt $@; \
 	else \
-	  cp $(srcdir)/lex.c $@ && echo $@ copied.; \
+	  gperf -C -p -j1 -i 1 -g -o -t -N rb_reserved_word -k1,3,$$ $? > $@.tmp && \
+	  mv $@.tmp $@ && \
+	  cp $? $(srcdir)/lex.c.src && \
+	  cp $@ $(srcdir)/lex.c.blt; \
 	fi
 
 .y.c:
diff --git a/bcc32/Makefile.sub b/bcc32/Makefile.sub
index c98876fac1..042debf315 100644
--- a/bcc32/Makefile.sub
+++ b/bcc32/Makefile.sub
@@ -482,6 +482,9 @@ $(RUBY_INSTALL_NAME).rc $(RUBYW_INSTALL_NAME).rc $(RUBY_SO_NAME).rc: rbconfig.rb
 			-so_name=$(RUBY_SO_NAME) \
 			. $(icondirs) $(srcdir)/win32
 
+lex.c: {$(srcdir)}lex.c.blt
+	copy "$(?:/=\)" $@
+
 post-install-bin::
 	@$(NULLCMD)
 post-install-lib::
diff --git a/lex.c b/lex.c.blt
similarity index 100%
rename from lex.c
rename to lex.c.blt
diff --git a/lex.c.src b/lex.c.src
new file mode 100644
index 0000000000..8741eb46b7
--- /dev/null
+++ b/lex.c.src
@@ -0,0 +1,50 @@
+%{
+struct kwtable {char *name; int id[2]; enum lex_state_e state;};
+const struct kwtable *rb_reserved_word _((const char *, unsigned int));
+#ifndef RIPPER
+%}
+
+struct kwtable;
+%%
+__LINE__, {keyword__LINE__, keyword__LINE__}, EXPR_END
+__FILE__, {keyword__FILE__, keyword__FILE__}, EXPR_END
+BEGIN, {keyword_BEGIN, keyword_BEGIN}, EXPR_END
+END, {keyword_END, keyword_END}, EXPR_END
+alias, {keyword_alias, keyword_alias}, EXPR_FNAME
+and, {keyword_and, keyword_and}, EXPR_VALUE
+begin, {keyword_begin, keyword_begin}, EXPR_BEG
+break, {keyword_break, keyword_break}, EXPR_MID
+case, {keyword_case, keyword_case}, EXPR_VALUE
+class, {keyword_class, keyword_class}, EXPR_CLASS
+def, {keyword_def, keyword_def}, EXPR_FNAME
+defined?, {keyword_defined, keyword_defined}, EXPR_ARG
+do, {keyword_do, keyword_do}, EXPR_BEG
+else, {keyword_else, keyword_else}, EXPR_BEG
+elsif, {keyword_elsif, keyword_elsif}, EXPR_VALUE
+end, {keyword_end, keyword_end}, EXPR_END
+ensure, {keyword_ensure, keyword_ensure}, EXPR_BEG
+false, {keyword_false, keyword_false}, EXPR_END
+for, {keyword_for, keyword_for}, EXPR_VALUE
+if, {keyword_if, modifier_if}, EXPR_VALUE
+in, {keyword_in, keyword_in}, EXPR_VALUE
+module, {keyword_module, keyword_module}, EXPR_VALUE
+next, {keyword_next, keyword_next}, EXPR_MID
+nil, {keyword_nil, keyword_nil}, EXPR_END
+not, {keyword_not, keyword_not}, EXPR_VALUE
+or, {keyword_or, keyword_or}, EXPR_VALUE
+redo, {keyword_redo, keyword_redo}, EXPR_END
+rescue, {keyword_rescue, modifier_rescue}, EXPR_MID
+retry, {keyword_retry, keyword_retry}, EXPR_END
+return, {keyword_return, keyword_return}, EXPR_MID
+self, {keyword_self, keyword_self}, EXPR_END
+super, {keyword_super, keyword_super}, EXPR_ARG
+then, {keyword_then, keyword_then}, EXPR_BEG
+true, {keyword_true, keyword_true}, EXPR_END
+undef, {keyword_undef, keyword_undef}, EXPR_FNAME
+unless, {keyword_unless, modifier_unless}, EXPR_VALUE
+until, {keyword_until, modifier_until}, EXPR_VALUE
+when, {keyword_when, keyword_when}, EXPR_VALUE
+while, {keyword_while, modifier_while}, EXPR_VALUE
+yield, {keyword_yield, keyword_yield}, EXPR_ARG
+%%
+#endif
diff --git a/win32/Makefile.sub b/win32/Makefile.sub
index efdeaae049..3cdf43207e 100644
--- a/win32/Makefile.sub
+++ b/win32/Makefile.sub
@@ -575,6 +575,9 @@ $(RUBY_INSTALL_NAME).rc $(RUBYW_INSTALL_NAME).rc $(RUBY_SO_NAME).rc: $(RBCONFIG)
 .rc.res:
 	$(RC) -I. -I$(<D) $(iconinc) -I$(srcdir)/win32 $(RFLAGS) -fo$@ $(<:\=/)
 
+lex.c: {$(srcdir)}lex.c.blt
+	copy $(?:/=\) $@
+
 {$(srcdir)}.y.c:
 	$(YACC) $(YFLAGS) $(<:\=/)
 	sed -e "s!^ *extern char \*getenv();!/* & */!;s/^\(#.*\)y\.tab/\1parse/" y.tab.c > $@
diff --git a/wince/Makefile.sub b/wince/Makefile.sub
index 56ee9050cd..8107c75b13 100644
--- a/wince/Makefile.sub
+++ b/wince/Makefile.sub
@@ -527,6 +527,9 @@ end
 .rc.res:
 	$(RC) -I. -I$(<D) $(iconinc) -I$(srcdir)/win32 $(RFLAGS) -fo$@ $(<:\=/)
 
+lex.c: {$(srcdir)}lex.c.blt
+	copy $(?:/=\) $@
+
 {$(srcdir)}.y.c:
 	$(YACC) $(YFLAGS) $(<:\=/)
 	sed -e "s!^ *extern char \*getenv();!/* & */!;s/^\(#.*\)y\.tab/\1parse/" y.tab.c > $@