diff --git a/ChangeLog b/ChangeLog
index aa75b5a5b7..062b8f4bd6 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Sun May 11 17:57:36 2008  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* configure.in (MINIRUBY): should not include extension library path.
+
 Sun May 11 10:36:10 2008  Kazuhiro NISHIYAMA  <zn@mbf.nifty.com>
 
 	* eval.c (method_name, method_owner): New methods; backported
diff --git a/configure.in b/configure.in
index 55600b37e4..0dd53a9e90 100644
--- a/configure.in
+++ b/configure.in
@@ -1402,6 +1402,7 @@ if test x"$cross_compiling" = xyes; then
   RUNRUBY='$(MINIRUBY) -I`cd $(srcdir)/lib; pwd`'
 else
   MINIRUBY='./miniruby$(EXEEXT) -I$(srcdir)/lib'
+  MINIRUBY="$MINIRUBY"' -I$(EXTOUT)/common -I./- -r$(srcdir)/ext/purelib.rb'
   PREP='miniruby$(EXEEXT)'
   RUNRUBY='$(MINIRUBY) $(srcdir)/runruby.rb --extout=$(EXTOUT)'
 fi
diff --git a/ext/purelib.rb b/ext/purelib.rb
index 10ee06176c..284254a8b4 100644
--- a/ext/purelib.rb
+++ b/ext/purelib.rb
@@ -1,3 +1,3 @@
-if nul = $:.index("-")
+if nul = $:.find_index {|path| /\A(?:\.\/)*-\z/ =~ path}
   $:[nul..-1] = ["."]
 end