diff --git a/ChangeLog b/ChangeLog
index 693b2b60b9..8d9203e5a1 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,4 +1,6 @@
-Thu Jul 22 12:30:52 2010  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+Thu Jul 22 12:58:12 2010  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* configure.in (RUBY_EXTERN): ignore invalid attribute.
 
 	* configure.in: fix for older autoconf.
 
diff --git a/configure.in b/configure.in
index 28356b50e8..7c43cab170 100644
--- a/configure.in
+++ b/configure.in
@@ -676,6 +676,21 @@ EOH
 ])dnl
 ])dnl
 
+AC_DEFUN([RUBY_WERROR_FLAG], [dnl
+if test "${ac_c_werror_flag+set}"; then
+  rb_c_werror_flag="$ac_c_werror_flag"
+else
+  unset rb_c_werror_flag
+fi
+ac_c_werror_flag=yes
+$1
+if test "${rb_c_werror_flag+set}"; then
+  ac_c_werror_flag="$rb_c_werror_flag"
+else
+  unset ac_c_werror_flag
+fi])
+
+dnl RUBY_FUNC_ATTRIBUTE(attrib, macroname, cachevar, condition)
 AC_DEFUN([RUBY_FUNC_ATTRIBUTE], [dnl
 m4_ifval([$2], dnl
   [AS_VAR_PUSHDEF([attrib],[$2])], dnl
@@ -688,12 +703,7 @@ m4_ifval([$3], dnl
 m4_ifval([$4], [rbcv_cond=[$4]; test "$rbcv_cond" || unset rbcv_cond])
 AC_CACHE_CHECK(for [$1] function attribute, rbcv,
 [rbcv=x
-if test "${ac_c_werror_flag+set}"; then
-  rb_c_werror_flag="$ac_c_werror_flag"
-else
-  unset rb_c_werror_flag
-fi
-ac_c_werror_flag=yes
+RUBY_WERROR_FLAG([
 for mac in "__attribute__ (($1)) x" "x __attribute__ (($1))" "__declspec($1) x" x; do
   m4_ifval([$4],mac="$mac"${rbcv_cond+" /* only if $rbcv_cond */"})
   AC_TRY_COMPILE(
@@ -705,12 +715,7 @@ ${rbcv_cond+[@%:@endif]})
     attrib[(void conftest_attribute_check(void));], [],
     [rbcv="$mac"; break])
 done
-if test "${rb_c_werror_flag+set}"; then
-  ac_c_werror_flag="$rb_c_werror_flag"
-else
-  unset ac_c_werror_flag
-fi
-])
+])])
 if test "$rbcv" != x; then
     RUBY_DEFINE_IF([${rbcv_cond}], attrib[(x)], $rbcv)
 fi
@@ -745,12 +750,14 @@ fi
 
 AC_CACHE_CHECK([for RUBY_EXTERN], rb_cv_ruby_extern,
 [rb_cv_ruby_extern=no
+RUBY_WERROR_FLAG([
 for mac in "__attribute__((dllimport))" "__declspec(dllimport)"; do
   AC_TRY_COMPILE(
     [extern $mac void conftest(void);],
     [conftest();],
     [rb_cv_ruby_extern="extern $mac"; break])
 done])
+])
 test "x$rb_cv_ruby_extern" = xno || AC_DEFINE_UNQUOTED(RUBY_EXTERN, $rb_cv_ruby_extern)
 
 RUBY_APPEND_OPTION(XCFLAGS, -DRUBY_EXPORT)