diff --git a/ChangeLog b/ChangeLog
index c624bac06c..5906557ba6 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+Thu Jan 20 23:44:00 2011  KOSAKI Motohiro  <kosaki.motohiro@gmail.com>
+
+	* configure.in: Fix rb_cv_va_args_macro was broken. We are using
+	  -Werror=implicit-function-declaration compile option. therefore
+	  we need a function declaration explicitly.
+
 Thu Jan 20 23:58:02 2011  Tanaka Akira  <akr@fsij.org>
 
 	* node.h: parenthesize macro arguments.
diff --git a/configure.in b/configure.in
index c25296639c..7d9bf1c06b 100644
--- a/configure.in
+++ b/configure.in
@@ -760,8 +760,10 @@ if test "$rb_cv_stdarg" = yes; then
 fi
 
 AC_CACHE_CHECK(for variable length macro, rb_cv_va_args_macro,
-  [AC_TRY_COMPILE([@%:@define FOO(a, ...) foo(a, @%:@@%:@__VA_ARGS__)],
-  [FOO(1);FOO(1,2);FOO(1,2,3);],
+  [AC_TRY_COMPILE([
+int foo(int x, ...);
+@%:@define FOO(a, ...) foo(a, @%:@@%:@__VA_ARGS__)
+], [FOO(1);FOO(1,2);FOO(1,2,3);],
   rb_cv_va_args_macro=yes,
   rb_cv_va_args_macro=no)])
 if test "$rb_cv_va_args_macro" = yes; then