diff --git a/ChangeLog b/ChangeLog
index 3cf8e0ff59..b67d3cf513 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,4 +1,6 @@
-Fri Aug  8 16:44:40 2008  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+Fri Aug  8 16:52:55 2008  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* common.mk (enc.mk): mkmf.rb requires rbconfig.rb.
 
 	* common.mk (srcs-enc): renamed from transcodes.
 
diff --git a/common.mk b/common.mk
index ad40ce4174..8476d46062 100644
--- a/common.mk
+++ b/common.mk
@@ -380,7 +380,7 @@ encs: enc.mk $(LIBRUBY) $(PREP)
 	$(MAKE) -f enc.mk RUBY="$(MINIRUBY)" $(MFLAGS)
 
 enc.mk: $(srcdir)/enc/make_encmake.rb $(srcdir)/enc/Makefile.in $(srcdir)/enc/depend \
-	$(srcdir)/lib/mkmf.rb $(PREP)
+	$(srcdir)/lib/mkmf.rb $(RBCONFIG)
 	$(MINIRUBY) $(srcdir)/enc/make_encmake.rb --builtin-encs="$(BUILTIN_ENCOBJS)" $@
 
 .PRECIOUS: $(MKFILES)