diff --git a/ChangeLog b/ChangeLog
index 776d39b6c0..8b4baddea0 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+Fri Jun  8 11:54:18 2007  Tanaka Akira  <akr@fsij.org>
+
+	* lex.c.blt: moved from lex.c.
+
+	* Makefile.in: use lex.c.blt if gperf is not available.
+
 Thu Jun  7 21:38:39 2007  Koichi Sasada  <ko1@atdot.net>
 
 	* thread.c (rb_thread_execute_interrupts): invoke ensure when
diff --git a/Makefile.in b/Makefile.in
index 5a65d34a04..4dba2db716 100644
--- a/Makefile.in
+++ b/Makefile.in
@@ -160,9 +160,12 @@ $(srcdir)/configure: $(srcdir)/configure.in
 		cd $(srcdir) && $(AUTOCONF)
 
 lex.c: keywords
-	@-$(RM) $@
-	gperf -C -p -j1 -i 1 -g -o -t -N rb_reserved_word -k1,3,$$ $? > $@ || \
-	cp "$(srcdir)/$@" .
+	( \
+	  gperf -C -p -j1 -i 1 -g -o -t -N rb_reserved_word -k1,3,$$ $? > $@.tmp && \
+	  cp $@.tmp $@ && \
+	  mv $@.tmp "$(srcdir)/$@.blt" \
+	) || \
+	cp "$(srcdir)/$@.blt" $@
 
 .y.c:
 	$(YACC) $(YFLAGS) -o $@ $<
diff --git a/lex.c b/lex.c.blt
similarity index 100%
rename from lex.c
rename to lex.c.blt