diff --git a/ChangeLog b/ChangeLog
index 370eed3ff6..5b8f211822 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,7 +1,6 @@
 Thu Dec 11 23:48:00 2008  Tadayoshi Funaba  <tadf@dotrb.org>
 
-	* lib/cmath.rb (sqrt): should pass nan or infinity to the original
-	  method.
+	* lib/cmath.rb (sqrt): should pass nan to the original method.
 
 Thu Dec 11 21:04:04 2008  Kouhei Sutou  <kou@cozmixng.org>
 
diff --git a/lib/cmath.rb b/lib/cmath.rb
index 9705b277b0..95a30c336b 100644
--- a/lib/cmath.rb
+++ b/lib/cmath.rb
@@ -57,10 +57,10 @@ module CMath
 
   def sqrt(z)
     if z.real?
-      if z >= 0 || (Float === z && (z.nan? || z.infinite?))
-	sqrt!(z)
-      else
+      if z < 0
 	Complex(0, sqrt!(-z))
+      else
+	sqrt!(z)
       end
     else
       if z.imag < 0