2 files changed, 6 insertions, 0 deletions
diff --git a/ChangeLog b/ChangeLog
index ff5d3eb392..09bedb241c 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Tue Dec 23 15:46:43 2008  Yuki Sonoda (Yugui)  <yugui@yugui.jp>
+
+	* lib/mathn.rb: Math.sqrt(NaN) should be NaN. [ruby-dev:37537]
+
 Tue Dec 23 15:46:47 2008  Eric Hodel  <drbrain@segment7.net>
 	* gem_prelude.rb:  Match full RubyGems behavior when a gem can't be
 	  found.
diff --git a/lib/mathn.rb b/lib/mathn.rb
index 48cb99f8c6..0241f578e9 100644
--- a/lib/mathn.rb
+++ b/lib/mathn.rb
@@ -134,6 +134,8 @@ module Math
       else
 	Complex(x, -y)
       end
+    elsif a.respond_to?(:nan?) and a.nan?
+      a
     elsif a >= 0
       rsqrt(a)
     else