diff --git a/ChangeLog b/ChangeLog
index 0649103567..0bb653e3b9 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Thu Jan  3 18:39:12 2008  Tanaka Akira  <akr@fsij.org>
+
+	* encoding.c: (rb_tolower, rb_toupper): body was exchanged.
+
 Thu Jan  3 17:54:01 2008  Tanaka Akira  <akr@fsij.org>
 
 	* regenc.h (onigenc_ascii_is_code_ctype): put back.
diff --git a/encoding.c b/encoding.c
index 27fda8d76f..fcb40795cf 100644
--- a/encoding.c
+++ b/encoding.c
@@ -1039,12 +1039,12 @@ int rb_isxdigit(int c) { return ctype_test(c, ONIGENC_CTYPE_XDIGIT); }
 int
 rb_tolower(int c)
 {
-    return rb_isascii(c) ? ONIGENC_ASCII_CODE_TO_UPPER_CASE(c) : c;
+    return rb_isascii(c) ? ONIGENC_ASCII_CODE_TO_LOWER_CASE(c) : c;
 }
 
 int
 rb_toupper(int c)
 {
-    return rb_isascii(c) ? ONIGENC_ASCII_CODE_TO_LOWER_CASE(c) : c;
+    return rb_isascii(c) ? ONIGENC_ASCII_CODE_TO_UPPER_CASE(c) : c;
 }