diff --git a/ChangeLog b/ChangeLog
index 91fc24e4d3..bdd80a60d8 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Tue May 28 11:30:02 2013  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* ext/extmk.rb (extmake): leave makefiles untouched if the content is
+	  not changed, to get rid of unnecessary re-linking.
+
 Tue May 28 03:11:02 2013  Koichi Sasada  <ko1@atdot.net>
 
 	* ext/objspace/gc_hook.c, ext/objspace/objspace.c: add new methods to
diff --git a/ext/extmk.rb b/ext/extmk.rb
index eda487c30e..1ca5efd52c 100755
--- a/ext/extmk.rb
+++ b/ext/extmk.rb
@@ -222,14 +222,14 @@ def extmake(target)
     ok &&= File.open(makefile){|f| !f.gets[DUMMY_SIGNATURE]}
     ok = yield(ok) if block_given?
     if ok
-      open(makefile, "r+") do |f|
-        s = f.read.sub!(/^(static:)\s.*/, '\1 all')
+      open(makefile, "r+b") do |f|
+        s = f.read.sub!(/^(static:)\s(?!all\b).*/, '\1 all') or break
         f.rewind
         f.print(s)
         f.truncate(f.pos)
       end
     else
-      open(makefile, "w") do |f|
+      open(makefile, "wb") do |f|
         f.puts "# " + DUMMY_SIGNATURE
 	f.print(*dummy_makefile(CONFIG["srcdir"]))
       end