diff --git a/ChangeLog b/ChangeLog
index 56f24fae16..0d4ecb066c 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Wed Mar  7 14:26:11 2001  WATANABE Hirofumi  <eban@ruby-lang.org>
+
+	* math.c (math_log, math_log10): should return NaN if x < 0.0
+	  on Cygwin.
+
 Tue Mar  6 10:50:29 2001  Yukihiro Matsumoto  <matz@ruby-lang.org>
 
 	* parse.y (primary): rescue and ensure clauses should be allowed
diff --git a/math.c b/math.c
index a676abf45f..9b28ddbf60 100644
--- a/math.c
+++ b/math.c
@@ -64,6 +64,11 @@ math_exp(obj, x)
     return rb_float_new(exp(RFLOAT(x)->value));
 }
 
+#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))
+#endif
+
 static VALUE
 math_log(obj, x)
     VALUE obj, x;
diff --git a/version.h b/version.h
index 00adc3fad7..588e9dd99d 100644
--- a/version.h
+++ b/version.h
@@ -1,4 +1,4 @@
 #define RUBY_VERSION "1.7.0"
-#define RUBY_RELEASE_DATE "2001-03-06"
+#define RUBY_RELEASE_DATE "2001-03-07"
 #define RUBY_VERSION_CODE 170
-#define RUBY_RELEASE_CODE 20010306
+#define RUBY_RELEASE_CODE 20010307