diff --git a/ChangeLog b/ChangeLog
index 455d029f1d..187157498c 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Fri Nov  6 17:13:45 2009  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* lib/mkmf.rb (create_header): split the line by tabs.
+
 Fri Nov  6 12:02:32 2009  NARUSE, Yui  <naruse@ruby-lang.org>
 
 	* configure.in (MINIDLNOBJ): set default as dmydln.o.
diff --git a/lib/mkmf.rb b/lib/mkmf.rb
index 815672b053..7635b4b7a3 100644
--- a/lib/mkmf.rb
+++ b/lib/mkmf.rb
@@ -1264,7 +1264,7 @@ def create_header(header = "extconf.h")
   for line in $defs
     case line
     when /^-D([^=]+)(?:=(.*))?/
-      hdr << "#define #$1 #{$2 ? Shellwords.shellwords($2)[0] : 1}\n"
+      hdr << "#define #$1 #{$2 ? Shellwords.shellwords($2)[0].gsub(/(?=\t+)/, "\\\n") : 1}\n"
     when /^-U(.*)/
       hdr << "#undef #$1\n"
     end