diff --git a/ChangeLog b/ChangeLog
index 580cc49255..3af2e62431 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Sun Jun 28 21:16:48 2009  Tadayoshi Funaba  <tadf@dotrb.org>
+
+	* lib/cmath.rb (sqrt): fixed an issue [ruby-list:45852].
+
 Sun Jun 28 19:48:29 2009  Tadayoshi Funaba  <tadf@dotrb.org>
 
 	* complex.c (nucomp_expt): some improvements.
diff --git a/lib/cmath.rb b/lib/cmath.rb
index d9e53f361a..6b47e70a15 100644
--- a/lib/cmath.rb
+++ b/lib/cmath.rb
@@ -63,7 +63,8 @@ module CMath
 	sqrt!(z)
       end
     else
-      if z.imag < 0
+      if z.imag < 0 ||
+	  (z.imag == 0 && z.imag.to_s[0] == '-')
 	sqrt(z.conjugate).conjugate
       else
 	r = z.abs