diff --git a/ChangeLog b/ChangeLog
index 0315699ef2..b55133f937 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+Thu Sep 24 09:41:42 2009  Marc-Andre Lafortune  <ruby-core@marc-andre.ca>
+
+	* lib/mathn.rb (Bignum#**): Fixed bignum**fixnum that was broken when
+	  requiring lib/mathn
+	  [ruby-core:25740]
+
 Thu Sep 24 02:21:23 2009  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* ext/bigdecimal/lib/bigdecimal/math.rb (atan): atan(Infinity) is
diff --git a/lib/mathn.rb b/lib/mathn.rb
index 57eac113c7..f834893f3f 100644
--- a/lib/mathn.rb
+++ b/lib/mathn.rb
@@ -25,7 +25,7 @@ class Fixnum
   remove_method :/
   alias / quo
 
-  alias power! ** unless defined?(0.power!)
+  alias power! ** unless method_defined? :power!
 
   def ** (other)
     if self < 0 && other.round != other
@@ -41,7 +41,7 @@ class Bignum
   remove_method :/
   alias / quo
 
-  alias power! ** unless defined?(0.power!)
+  alias power! ** unless method_defined? :power!
 
   def ** (other)
     if self < 0 && other.round != other
diff --git a/lib/rational.rb b/lib/rational.rb
index 515c273d54..a1aeca1e40 100644
--- a/lib/rational.rb
+++ b/lib/rational.rb
@@ -7,7 +7,7 @@ class Fixnum
   alias quof fdiv
   alias rdiv quo
 
-  alias power! ** unless defined?(0.power!)
+  alias power! ** unless method_defined? :power!
   alias rpower **
 
 end
@@ -17,7 +17,7 @@ class Bignum
   alias quof fdiv
   alias rdiv quo
 
-  alias power! ** unless defined?(0.power!)
+  alias power! ** unless method_defined? :power!
   alias rpower **
 
 end