diff --git a/ChangeLog b/ChangeLog
index bf097e1c2a..68262ca52e 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Wed May 12 15:04:57 2010  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* ext/bigdecimal/lib/bigdecimal/math.rb (BigMath#log): improved
+	  precision and performance. [ruby-dev:41295]
+
 Tue May 11 14:26:00 2010  Kenta Murata <mrkn@mrkn.jp>
 
 	* ext/bigdecimal/lib/bigdecimal/math.rb (atan),
diff --git a/ext/bigdecimal/lib/bigdecimal/math.rb b/ext/bigdecimal/lib/bigdecimal/math.rb
index 07efcbe099..41fc69f66c 100644
--- a/ext/bigdecimal/lib/bigdecimal/math.rb
+++ b/ext/bigdecimal/lib/bigdecimal/math.rb
@@ -190,8 +190,10 @@ module BigMath
     one = BigDecimal("1")
     two = BigDecimal("2")
     n  = prec + BigDecimal.double_fig
-    if (expo = x.exponent) < 0
+    if (expo = x.exponent) < 0 || expo >= 3
       x = x.mult(BigDecimal("1E#{-expo}"), n)
+    else
+      expo = nil
     end
     x  = (x - one).div(x + one,n)
     x2 = x.mult(x,n)
@@ -206,7 +208,7 @@ module BigMath
       y += d
     end
     y *= two
-    if expo < 0
+    if expo
       y += log(BigDecimal("10"),prec) * BigDecimal(expo.to_s)
     end
     y
diff --git a/version.h b/version.h
index be78dc9541..35e4b343ca 100644
--- a/version.h
+++ b/version.h
@@ -1,5 +1,5 @@
 #define RUBY_VERSION "1.9.2"
-#define RUBY_RELEASE_DATE "2010-05-11"
+#define RUBY_RELEASE_DATE "2010-05-12"
 #define RUBY_PATCHLEVEL -1
 
 #define RUBY_VERSION_MAJOR 1
@@ -7,7 +7,7 @@
 #define RUBY_VERSION_TEENY 1
 #define RUBY_RELEASE_YEAR 2010
 #define RUBY_RELEASE_MONTH 5
-#define RUBY_RELEASE_DAY 11
+#define RUBY_RELEASE_DAY 12
 
 #include "ruby/version.h"