diff --git a/ChangeLog b/ChangeLog
index 278d921693..814b4f937e 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Thu May 24 16:08:21 2001  WATANABE Hirofumi  <eban@ruby-lang.org>
+
+	* mkconfig.rb: autoconf 2.50 support.
+
 Thu May 24 14:23:35 2001  Yukihiro Matsumoto  <matz@ruby-lang.org>
 
 	* eval.c (rb_yield_0): need argument adjustment for C defined
diff --git a/mkconfig.rb b/mkconfig.rb
index 721cd3f67d..14e5829f53 100644
--- a/mkconfig.rb
+++ b/mkconfig.rb
@@ -48,7 +48,7 @@ File.foreach "config.status" do |line|
       v_others << v
     end
     has_version = true if name == "MAJOR"
-  elsif /^ac_given_srcdir=(.*)/ =~ line
+  elsif /^(?:ac_given_)srcdir=(.*)/ =~ line
     v_fast << "  CONFIG[\"srcdir\"] = \"" + File.expand_path($1) + "\"\n"
     has_srcdir = true
   elsif /^ac_given_INSTALL=(.*)/ =~ line
@@ -58,7 +58,7 @@ File.foreach "config.status" do |line|
 end
 
 if not has_srcdir
-  v_fast << "  CONFIG[\"srcdir\"] = \"" + File.expand_path(srcdir) + "\"\n"
+  v_fast << "  CONFIG[\"srcdir\"] = \"" + File.expand_path(srcdir || '.') + "\"\n"
 end
 
 if not has_version