diff --git a/ChangeLog b/ChangeLog
index 6a6128aeae..0661dd980a 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,7 +1,10 @@
-Sun Jul  9 18:04:14 2006  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+Sun Jul  9 18:06:47 2006  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* lib/mkmf.rb (try_constant): fix for value 1 at cross compiling.
 
+	* lib/mkmf.rb (create_makefile): prevent substitution of macro
+	  definition.  fixed: http://www.yotabanana.com/lab/20060624.html#p02
+
 Sun Jul  9 07:58:48 2006  Ryan Davis  <ryand@zenspider.com>
 
 	* lib/rdoc/parsers/parse_f95.rb: massive overhaul from Yasuhiro
diff --git a/lib/mkmf.rb b/lib/mkmf.rb
index c72388ab6a..497a14424b 100644
--- a/lib/mkmf.rb
+++ b/lib/mkmf.rb
@@ -1248,7 +1248,7 @@ site-install-rb: install-rb
 	  suffixes << m[1] << m[2]
 	  implicit = [[m[1], m[2]], [m.post_match]]
 	  next
-	elsif RULE_SUBST and /\A[$\w][^#]*:/ =~ line
+	elsif RULE_SUBST and /\A(?!\s*\w+\s*=)[$\w][^#]*:/ =~ line
 	  line.gsub!(%r"(?<=\s)(?!\.)([^$(){}+=:\s\/\\,]+)(?=\s|\z)") {|*m| RULE_SUBST % m}
 	end
 	depout << line