diff --git a/ext/opencv/cvcontourtree.cpp b/ext/opencv/cvcontourtree.cpp
index 382c4e1..90a1435 100644
--- a/ext/opencv/cvcontourtree.cpp
+++ b/ext/opencv/cvcontourtree.cpp
@@ -14,11 +14,11 @@
  * Contour tree. CvContour#create_tree
  *
  * C structure is here.
- *  typedef struct CvContourTree{
+ *  typedef struct CvContourTree {
  *    CV_SEQUENCE_FIELDS()
  *    CvPoint p1;
  *    CvPoint p2;
- *  }CvContourTree;
+ *  } CvContourTree;
  * 
  */
 __NAMESPACE_BEGIN_OPENCV
@@ -49,8 +49,7 @@ define_ruby_class()
   rb_klass = rb_define_class_under(opencv, "CvContourTree", cvseq);
   rb_define_method(rb_klass, "p1", RUBY_METHOD_FUNC(rb_p1), 0);
   rb_define_method(rb_klass, "p2", RUBY_METHOD_FUNC(rb_p2), 0);
-  rb_define_method(rb_klass, "contour", RUBY_METHOD_FUNC(rb_contour), 0);
-
+  rb_define_method(rb_klass, "contour", RUBY_METHOD_FUNC(rb_contour), 1);
 }
 
 VALUE
@@ -74,13 +73,17 @@ rb_p2(VALUE self)
  * used for reconstruction, so it is possible to build approximated contour.
  */
 VALUE
-rb_contour(int argc, VALUE *argv, VALUE self)
+rb_contour(VALUE self, VALUE criteria)
 {
-  VALUE criteria, storage;
-  rb_scan_args(argc, argv, "01", &criteria);
-  storage = cCvMemStorage::new_object();
-  CvSeq *contour = cvContourFromContourTree(CVCONTOURTREE(self), CVMEMSTORAGE(storage),
-					    VALUE_TO_CVTERMCRITERIA(criteria));
+  VALUE storage = cCvMemStorage::new_object();
+  CvSeq *contour = NULL;
+  try {
+    contour = cvContourFromContourTree(CVCONTOURTREE(self), CVMEMSTORAGE(storage),
+				       VALUE_TO_CVTERMCRITERIA(criteria));
+  }
+  catch (cv::Exception& e) {
+    raise_cverror(e);
+  }
   return cCvSeq::new_sequence(cCvContour::rb_class(), contour, cCvPoint::rb_class(), storage);
 }
 
diff --git a/ext/opencv/cvcontourtree.h b/ext/opencv/cvcontourtree.h
index 1b2f900..685500f 100644
--- a/ext/opencv/cvcontourtree.h
+++ b/ext/opencv/cvcontourtree.h
@@ -11,7 +11,7 @@
 #define RUBY_OPENCV_CVCONTOURTREE_H
 #include "opencv.h"
 
-#define __NAMESPACE_BEGIN_CVCONTOURTREE namespace cCvContourTree{
+#define __NAMESPACE_BEGIN_CVCONTOURTREE namespace cCvContourTree {
 #define __NAMESPACE_END_CVCONTOURTREE }
 
 __NAMESPACE_BEGIN_OPENCV
@@ -23,7 +23,7 @@ void define_ruby_class();
 
 VALUE rb_p1(VALUE self);
 VALUE rb_p2(VALUE self);
-VALUE rb_contour(int argc, VALUE *argv, VALUE self);
+VALUE rb_contour(VALUE self, VALUE criteria);
 
 VALUE new_object();
 
diff --git a/test/test_cvcontour.rb b/test/test_cvcontour.rb
index def6de0..57dd53b 100755
--- a/test/test_cvcontour.rb
+++ b/test/test_cvcontour.rb
@@ -58,7 +58,16 @@ class TestCvContour < OpenCVTestCase
   end
 
   def test_create_tree
-    flunk('FIXME: CvContour#create_tree is not tested yet.')
+    mat0 = create_cvmat(128, 128, :cv8u, 1) { |j, i|
+      (j - 64) ** 2 + (i - 64) ** 2 <= (32 ** 2) ? CvColor::White : CvColor::Black
+    }
+    contour = mat0.find_contours
+    tree = contour.create_tree
+    assert_equal(CvContourTree, tree.class)
+    assert_equal(34, tree.p1.x)
+    assert_equal(53, tree.p1.y)
+    assert_equal(0, tree.p2.x)
+    assert_equal(0, tree.p2.y)
   end
 
   def test_in
diff --git a/test/test_cvcontourtree.rb b/test/test_cvcontourtree.rb
new file mode 100755
index 0000000..c4ffd97
--- /dev/null
+++ b/test/test_cvcontourtree.rb
@@ -0,0 +1,43 @@
+#!/usr/bin/env ruby
+# -*- mode: ruby; coding: utf-8-unix -*- 
+require 'test/unit'
+require 'opencv'
+require File.expand_path(File.dirname(__FILE__)) + '/helper'
+
+include OpenCV
+
+# Tests for OpenCV::CvContourTree
+class TestCvContourTree < OpenCVTestCase
+  def setup
+    @tree = CvContourTree.new(CvPoint)
+  end
+
+  def test_initialize
+    tree = CvContourTree.new(CvPoint)
+    assert_equal(CvContourTree, tree.class)
+    assert(tree.is_a? CvSeq)
+  end
+
+  def test_p1
+    assert_equal(CvPoint, @tree.p1.class)
+  end
+
+  def test_p2
+    assert_equal(CvPoint, @tree.p2.class)
+  end
+
+  def test_contour
+    mat0 = create_cvmat(128, 128, :cv8u, 1) { |j, i|
+      (j - 64) ** 2 + (i - 64) ** 2 <= (32 ** 2) ? CvColor::White : CvColor::Black
+    }
+    contour = mat0.find_contours
+    tree = contour.create_tree
+    contour = tree.contour(CvTermCriteria.new(100, 0.01))
+    assert_equal(CvContour, contour.class)
+
+    assert_raise(CvStsBadArg) {
+      tree.contour(CvTermCriteria.new(0, 0))
+    }
+  end
+end
+