diff --git a/ChangeLog b/ChangeLog
index 7a2eb6ae5a..331b88608b 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Sat Mar 10 02:34:18 2001  WATANABE Hirofumi  <eban@ruby-lang.org>
+
+	* math.c (math_log, math_log10): use nan() instead of 0.0/0.0 on Cygwin.
+
 Thu Mar  8 17:43:59 2001  Minero Aoki  <aamine@dp.u-netsurf.ne.jp>
 
 	* lib/net/protocol.rb: one write(2) per one line.
diff --git a/math.c b/math.c
index 6bdc7422e1..2cac83e938 100644
--- a/math.c
+++ b/math.c
@@ -65,8 +65,8 @@ math_exp(obj, x)
 }
 
 #if defined __CYGWIN__
-#define log(x) ((x) < 0.0 ? 0.0 / 0.0 : log(x))
-#define log10(x) ((x) < 0.0 ? 0.0 / 0.0 : log10(x))
+#define log(x) ((x) < 0.0 ? nan() : log(x))
+#define log10(x) ((x) < 0.0 ? nan() : log10(x))
 #endif
 
 static VALUE
diff --git a/version.h b/version.h
index c7f3400043..0736027bc1 100644
--- a/version.h
+++ b/version.h
@@ -1,4 +1,4 @@
 #define RUBY_VERSION "1.6.3"
-#define RUBY_RELEASE_DATE "2001-03-07"
+#define RUBY_RELEASE_DATE "2001-03-10"
 #define RUBY_VERSION_CODE 163
-#define RUBY_RELEASE_CODE 20010307
+#define RUBY_RELEASE_CODE 20010310