diff --git a/lib/method_extensions.rb b/lib/method_extensions.rb
index da5412c..e6f4d4b 100644
--- a/lib/method_extensions.rb
+++ b/lib/method_extensions.rb
@@ -1,3 +1,4 @@
 require "method_extensions/method/source_with_doc"
+require "method_extensions/source_not_found_error"
 # We don't require `super` by default since it patches core methods
-# require "method_extensions/method/super"
\ No newline at end of file
+# require "method_extensions/method/super"
diff --git a/lib/method_extensions/method/source_with_doc.rb b/lib/method_extensions/method/source_with_doc.rb
index 555ab7c..304b98b 100644
--- a/lib/method_extensions/method/source_with_doc.rb
+++ b/lib/method_extensions/method/source_with_doc.rb
@@ -9,7 +9,7 @@ module MethodExtensions
   module MethodSourceWithDoc
     # Returns method source by parsing the file returned by `Method#source_location`.
     #
-    # If method definition cannot be found `ArgumentError` exception is raised
+    # If method definition cannot be found `MethodExtensions::SourceNotFoundError` exception is raised
     # (this includes methods defined by `attr_accessor`, `module_eval` etc.).
     #
     # Sample IRB session:
@@ -57,7 +57,7 @@ def doc
     # ruby-1.9.2-head > irb_context.inspect_mode = false # turn off inspect mode so that we can view sources
     #
     # ruby-1.9.2-head > ActiveRecord::Base.method(:find).source_with_doc
-    # ArgumentError: failed to find method definition around the lines:
+    # MethodExtensions::SourceNotFoundError: failed to find method definition around the lines:
     #       delegate :find, :first, :last, :all, :destroy, :destroy_all, :exists?, :delete, :delete_all, :update, :update_all, :to => :scoped
     #       delegate :find_each, :find_in_batches, :to => :scoped
     #
@@ -124,7 +124,7 @@ def irb_inspect
 
       require "coderay"
       require "rdoc/ri/driver"
-      
+
       puts to_s
 
       if source_location
@@ -140,7 +140,7 @@ def irb_inspect
         # 2. probably need to detect other doc types?
         # 3. RDoc::Markup::ToAnsi formatter reflows to the 78 chars width which
         #    looks ugly
-        # 
+        #
         #  begin
         #    formatter = Class.new(RDoc::Markup::ToAnsi) do
         #      def wrap(text)
@@ -165,7 +165,7 @@ def irb_inspect
       rescue ArgumentError => e
         puts e.message
       end
-      
+
       nil
     end
 
@@ -206,8 +206,7 @@ def method_source
         if @method_source
           @method_source
         else
-          raise ArgumentError.new("failed to find method definition around the lines:\n" <<
-                  definition_lines.join("\n"))
+          raise SourceNotFoundError.new(definition_lines)
         end
       end
 
@@ -272,4 +271,4 @@ def on_sp(token)
       end
     end
   end
-end if ripper_available
\ No newline at end of file
+end if ripper_available
diff --git a/lib/method_extensions/source_not_found_error.rb b/lib/method_extensions/source_not_found_error.rb
new file mode 100644
index 0000000..ecf1fbb
--- /dev/null
+++ b/lib/method_extensions/source_not_found_error.rb
@@ -0,0 +1,9 @@
+module MethodExtensions
+  class SourceNotFoundError < ArgumentError
+    def initialize(lines)
+      message = "failed to find method definition around the lines: \n"
+      message << lines.join("\n")
+      super message
+    end
+  end
+end
diff --git a/method_extensions.gemspec b/method_extensions.gemspec
index 7da8326..ffc55aa 100644
--- a/method_extensions.gemspec
+++ b/method_extensions.gemspec
@@ -1,9 +1,9 @@
 lib = File.expand_path('../lib/', __FILE__)
 $:.unshift lib unless $:.include?(lib)
- 
+
 Gem::Specification.new do |s|
   s.name        = "method_extensions"
-  s.version     = "0.0.8"
+  s.version     = "0.0.9"
   s.authors     = ["Evgeniy Dolzhenko"]
   s.email       = ["dolzenko@gmail.com"]
   s.homepage    = "http://github.com/dolzenko/method_extensions"
@@ -11,4 +11,4 @@ Gem::Specification.new do |s|
   s.files       = Dir.glob("lib/**/*") + %w(method_extensions.gemspec)
 
   s.add_dependency "coderay", "0.9.3"
-end
\ No newline at end of file
+end