diff --git a/ChangeLog b/ChangeLog
index d24faa28c4..fb92bb1780 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Sat Jan  7 00:47:07 2012  CHIKANAGA Tomoyuki  <nagachika00@gmail.com>
+
+	* configure.in: always define CANONICALIZATION_FOR_MATHN.
+	  [ruby-dev:45100] [Bug #5852]
+
 Fri Jan  6 23:11:20 2012  Ayumu AIZAWA  <ayumu.aizawa@gmail.com>
 
 	* include/ruby/version.h: RUBY_API_VERSION 2.0.0
diff --git a/configure.in b/configure.in
index b9f3c7948f..905efd1c6b 100644
--- a/configure.in
+++ b/configure.in
@@ -86,9 +86,7 @@ RUBY_PROGRAM_VERSION=`sed -n 's/^#define RUBY_VERSION "\(.*\)"/\1/p' $srcdir/ver
 AC_SUBST(RUBY_PROGRAM_VERSION)
 RUBY_RELEASE_DATE=`sed -n 's/^#define RUBY_RELEASE_DATE "\(.*\)"/\1/p' $srcdir/version.h`
 AC_SUBST(RUBY_RELEASE_DATE)
-if test "$MAJOR" = "1"; then
-  AC_DEFINE(CANONICALIZATION_FOR_MATHN)
-fi
+AC_DEFINE(CANONICALIZATION_FOR_MATHN)
 dnl checks for alternative programs
 AC_CANONICAL_BUILD
 AC_ARG_WITH(gcc,