diff --git a/ChangeLog b/ChangeLog
index afff9606dd..11d4357dd6 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Wed Sep 25 17:46:46 2002  NAKAMURA Usaku <usa@ruby-lang.org>
+
+	* lib/mkmf.rb (libpathflag): restore ENV['LIB'] when some error occured.
+
 Mon Sep 23 23:22:43 2002  Nobuyoshi Nakada  <nobu.nokada@softhome.net>
 
 	* eval.c (rb_call0): must not clear ruby_current_node, or
diff --git a/lib/mkmf.rb b/lib/mkmf.rb
index 04e6acdb6c..f27a7faf2f 100644
--- a/lib/mkmf.rb
+++ b/lib/mkmf.rb
@@ -211,8 +211,11 @@ end
 def libpathflag
   if $mswin
     ENV['LIB'] = ($LIBPATH + [ORIG_LIBPATH]).join(';')
-    yield ""
-    ENV['LIB'] = ORIG_LIBPATH
+    begin
+      yield ""
+    ensure
+      ENV['LIB'] = ORIG_LIBPATH
+    end
   else
     yield $LIBPATH.map{|x| %Q[#{LIBPATHFLAG}"#{x}"]}.join
   end