diff --git a/ChangeLog b/ChangeLog
index d3173204ec..046387f151 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Fri Feb 17 09:56:22 2012  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* lib/mkmf.rb (create_header): log the content of header.
+
 Fri Feb 17 09:44:55 2012  NARUSE, Yui  <naruse@ruby-lang.org>
 
 	* tool/transcode-tblgen.rb (import_ucm): don't use \h because the
diff --git a/lib/mkmf.rb b/lib/mkmf.rb
index 5b32553da1..a29e5bafbd 100644
--- a/lib/mkmf.rb
+++ b/lib/mkmf.rb
@@ -352,11 +352,11 @@ module MakeMakefile
     end
   end
 
-  def log_src(src)
+  def log_src(src, heading="checked program was")
     src = src.split(/^/)
     fmt = "%#{src.size.to_s.size}d: %s"
     Logging::message <<"EOM"
-checked program was:
+#{heading}:
 /* begin */
 EOM
     src.each_with_index {|line, no| Logging::message fmt, no+1, line}
@@ -1557,7 +1557,8 @@ SRC
       end
     end
     hdr << "#endif\n"
-    hdr = hdr.join
+    hdr = hdr.join("")
+    log_src(hdr, "#{header} is")
     unless (IO.read(header) == hdr rescue false)
       open(header, "wb") do |hfile|
         hfile.write(hdr)