diff --git a/mrbgems/default.gembox b/mrbgems/default.gembox
index 64f05de10..65584681d 100644
--- a/mrbgems/default.gembox
+++ b/mrbgems/default.gembox
@@ -14,6 +14,9 @@ MRuby::GemBox.new do |conf|
   # Use standard Struct class
   conf.gem :core => "mruby-struct"
 
+  # Use Comparable module extension
+  conf.gem :core => "mruby-compar-ext"
+
   # Use Enumerable module extension
   conf.gem :core => "mruby-enum-ext"
 
diff --git a/mrbgems/mruby-compar-ext/mrbgem.rake b/mrbgems/mruby-compar-ext/mrbgem.rake
new file mode 100644
index 000000000..dcf584339
--- /dev/null
+++ b/mrbgems/mruby-compar-ext/mrbgem.rake
@@ -0,0 +1,5 @@
+MRuby::Gem::Specification.new('mruby-compar-ext') do |spec|
+  spec.license = 'MIT'
+  spec.author  = 'mruby developers'
+  spec.summary = 'Enumerable module extension'
+end
diff --git a/mrbgems/mruby-compar-ext/mrblib/compar.rb b/mrbgems/mruby-compar-ext/mrblib/compar.rb
new file mode 100644
index 000000000..d66f816ef
--- /dev/null
+++ b/mrbgems/mruby-compar-ext/mrblib/compar.rb
@@ -0,0 +1,31 @@
+module Comparable
+  ##
+  # Returns <i>min</i> if <i>obj</i> <code><=></code> <i>min</i> is less
+  # than zero, <i>max</i> if <i>obj</i> <code><=></code> <i>max</i> is
+  # greater than zero and <i>obj</i> otherwise.
+  #
+  #     12.clamp(0, 100)         #=> 12
+  #     523.clamp(0, 100)        #=> 100
+  #     -3.123.clamp(0, 100)     #=> 0
+  #
+  #     'd'.clamp('a', 'f')      #=> 'd'
+  #     'z'.clamp('a', 'f')      #=> 'f'
+  #
+  def clamp(min, max)
+    if (min <=> max) > 0
+      raise ArgumentError, "min argument must be smaller than max argument"
+    end
+    c = self <=> min
+    if c == 0
+      return self
+    elsif c < 0
+      return min
+    end
+    c = self <=> max
+    if c > 0
+      return max
+    else
+      return self
+    end
+  end
+end