diff --git a/ChangeLog b/ChangeLog
index da4dc17ccd..fce5156655 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Sun Oct 25 05:44:34 2009  Marc-Andre Lafortune  <ruby-core@marc-andre.ca>
+
+	* lib/matrix.rb (**): Optimization (up to 45% faster)
+
 Sat Oct 24 14:28:40 2009  Yukihiro Matsumoto  <matz@ruby-lang.org>
 
 	* hash.c (rb_hash_set_default_proc): checks arity of defalt_proc
diff --git a/lib/matrix.rb b/lib/matrix.rb
index b577ef3118..3c75751e37 100644
--- a/lib/matrix.rb
+++ b/lib/matrix.rb
@@ -642,18 +642,12 @@ class Matrix
         return Matrix.identity(self.column_size) if other == 0
         other = -other
       end
-      z = x
-      n = other  - 1
-      while n != 0
-        while (div, mod = n.divmod(2)
-               mod == 0)
-          x = x * x
-          n = div
-        end
-        z *= x
-        n -= 1
+      z = nil
+      loop do
+        z = z ? z * x : x if other[0] == 1
+        return z if (other >>= 1).zero?
+        x *= x
       end
-      z
     elsif other.kind_of?(Float) || defined?(Rational) && other.kind_of?(Rational)
       Matrix.Raise ErrOperationNotDefined, "**"
     else