diff --git a/ChangeLog b/ChangeLog
index 8428a30b74..f26411a5f9 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Tue Mar 10 04:43:19 2009  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* configure.in (RUBY_CHECK_SIZEOF): fix for fallback.
+
 Tue Mar 10 03:48:27 2009  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* ext/dl/callback/depend: fix for parallel build.
diff --git a/configure.in b/configure.in
index 5b01e0fa69..c183b08212 100644
--- a/configure.in
+++ b/configure.in
@@ -341,6 +341,7 @@ AC_CACHE_CHECK([char bit], [rb_cv_char_bit],
     [_AC_COMPUTE_INT_COMPILE([CHAR_BIT], [rb_cv_char_bit],
 	[AC_INCLUDES_DEFAULT([@%:@include <limits.h>])], [rb_cv_char_bit=8])])
 
+dnl RUBY_CHECK_SIZEOF [typename], [maybe same size types], [macros], [include]
 AC_DEFUN([RUBY_CHECK_SIZEOF],
 [if test "$universal_binary" = yes; then
 AC_CACHE_CHECK([size of $1], [AS_TR_SH([ac_cv_sizeof_$1])], [dnl
@@ -373,18 +374,19 @@ AC_CACHE_CHECK([size of $1], [AS_TR_SH([ac_cv_sizeof_$1])], [dnl
 	done
     done
     }])
-    _AC_COMPUTE_INT_COMPILE(AS_TR_CPP(SIZEOF_$1), [t], [AC_INCLUDES_DEFAULT([
-$cond
-@%:@else
+    _AC_COMPUTE_INT_COMPILE(AS_TR_CPP(SIZEOF_$1), [t], [AC_INCLUDES_DEFAULT([$4])]
+[${cond+$cond
+@%:@else}
 typedef $1 ac__type_sizeof_;
 @%:@define AS_TR_CPP(SIZEOF_$1) sizeof(ac__type_sizeof_)
-@%:@endif
+${cond+@%:@endif}
 @%:@ifndef AS_TR_CPP(SIZEOF_$1)
 @%:@define AS_TR_CPP(SIZEOF_$1) 0
-@%:@endif])], [unset t])
+@%:@endif], [unset t])
     if test ${t-0} != 0; then
 	AS_TR_SH(ac_cv_sizeof_$1)="${AS_TR_SH(ac_cv_sizeof_$1)+${AS_TR_SH(ac_cv_sizeof_$1)-} }${t}"
     fi
+    : ${AS_TR_SH(ac_cv_sizeof_$1)=0}
 ])
 {
     unset cond