diff --git a/lib/rhino.rb b/lib/rhino.rb
index 7c43dcd..783a29a 100644
--- a/lib/rhino.rb
+++ b/lib/rhino.rb
@@ -22,6 +22,7 @@ Rhino.extend Rhino::To
 
 require 'rhino/object'
 require 'rhino/context'
+require 'rhino/error'
 require 'rhino/rhino_ext'
 require 'rhino/ruby_object'
 require 'rhino/ruby_function'
diff --git a/lib/rhino/context.rb b/lib/rhino/context.rb
index 6279e3f..fa558e7 100644
--- a/lib/rhino/context.rb
+++ b/lib/rhino/context.rb
@@ -90,23 +90,18 @@ module Rhino
     # * <tt>source_name</tt> - associated name for this source code. Mainly useful for backtraces.
     # * <tt>line_number</tt> - associate this number with the first line of executing source. Mainly useful for backtraces
     def eval(source, source_name = "<eval>", line_number = 1)
-      self.open do
-        begin
-          scope = Rhino.to_javascript(@scope)
-          if IO === source || StringIO === source
-            result = @native.evaluateReader(scope, IOReader.new(source), source_name, line_number, nil)
-          else
-            result = @native.evaluateString(scope, source.to_s, source_name, line_number, nil)
-          end
-          Rhino.to_ruby(result)
-        rescue JS::RhinoException => e
-          raise JavascriptError, e
+      open do
+        if IO === source || StringIO === source
+          result = @native.evaluateReader(@scope, IOReader.new(source), source_name, line_number, nil)
+        else
+          result = @native.evaluateString(@scope, source.to_s, source_name, line_number, nil)
         end
+        Rhino.to_ruby(result)
       end
     end
-
+    
     def evaluate(*args) # :nodoc:
-      self.eval(*args)
+      eval(*args) # an alias
     end
 
     # Read the contents of <tt>filename</tt> and evaluate it as javascript. Returns the result of evaluating the
@@ -163,40 +158,50 @@ module Rhino
       end
     end
     
-    # Enter this context for operations. Some methods such as eval() will
-    # fail unless this context is open
-    def open
-      begin
-        @factory.enterContext(@native)
-        yield self
-      ensure
-        JS::Context.exit()
-      end if block_given?
+    # Enter this context for operations. 
+    # Some methods such as eval() will fail unless this context is open !
+    def open(&block)
+      do_open(&block)
+    rescue JS::RhinoException => e
+      raise Rhino::JSError.new(e)
     end
-
+    
+    private
+    
+      def do_open
+        begin
+          @factory.enterContext(@native)
+          yield self
+        ensure
+          JS::Context.exit
+        end      
+      end
+    
   end
 
-  class IOReader < java.io.Reader #:nodoc:
+  class IOReader < java.io.Reader # :nodoc:
 
     def initialize(io)
       @io = io
     end
 
-    def read(charbuffer, offset, length)
+    # implement int Reader#read(char[] buffer, int offset, int length)
+    def read(buffer, offset, length)
+      str = nil
       begin
         str = @io.read(length)
-        if str.nil?
-          return -1
-        else
-          jstring = java.lang.String.new(str)
-          for i in 0 .. jstring.length - 1
-            charbuffer[i + offset] = jstring.charAt(i)
-          end
-          return jstring.length
-        end
       rescue StandardError => e
         raise java.io.IOException.new, "Failed reading from ruby IO object"
       end
+      if str.nil?
+        return -1
+      else
+        jstr = str.to_java
+        for i in 0 .. jstr.length - 1
+          buffer[i + offset] = jstr.charAt(i)
+        end
+        return jstr.length
+      end
     end
     
   end
@@ -216,23 +221,7 @@ module Rhino
   class ContextError < StandardError # :nodoc:
   end
 
-  class JavascriptError < StandardError # :nodoc:
-    def initialize(native)
-      @native = native
-    end
-
-    def message
-      @native.cause.details
-    end
-
-    def javascript_backtrace
-      @native.getScriptStackTrace()
-    end
-  end
-
-  JSError = JavascriptError
-
-  class RunawayScriptError < StandardError # :nodoc:
+  class RunawayScriptError < ContextError # :nodoc:
   end
   
 end
diff --git a/lib/rhino/deprecations.rb b/lib/rhino/deprecations.rb
index 209e5e9..65592d8 100644
--- a/lib/rhino/deprecations.rb
+++ b/lib/rhino/deprecations.rb
@@ -8,6 +8,9 @@ module Rhino
     when 'J' then
       warn "[DEPRECATION] `Rhino::J` is deprecated, use `Rhino::JS` instead."
       return JS
+    when 'JavascriptError' then
+      warn "[DEPRECATION] `Rhino::JavascriptError` is deprecated, use `Rhino::JSError` instead."
+      return JSError
     when 'NativeObject' then
       warn "[DEPRECATION] `Rhino::NativeObject` is no longer used, returning a stub."
       return @@stub_class
diff --git a/lib/rhino/error.rb b/lib/rhino/error.rb
new file mode 100644
index 0000000..021d96e
--- /dev/null
+++ b/lib/rhino/error.rb
@@ -0,0 +1,25 @@
+
+module Rhino
+
+  class JSError < StandardError
+    
+    def initialize(native)
+      @native = native # NativeException wrapping a Java Throwable
+    end
+
+    # most likely a Rhino::JS::JavaScriptException
+    def cause
+      @native.respond_to?(:cause) ? @native.cause : nil
+    end
+    
+    def message
+      cause ? cause.details : @native.to_s
+    end
+
+    def javascript_backtrace
+      cause.is_a?(JS::RhinoException) ? cause.getScriptStackTrace : nil
+    end
+    
+  end
+  
+end
diff --git a/spec/rhino/deprecations_spec.rb b/spec/rhino/deprecations_spec.rb
index 060640a..eccf849 100644
--- a/spec/rhino/deprecations_spec.rb
+++ b/spec/rhino/deprecations_spec.rb
@@ -33,5 +33,9 @@ describe 'deprecations' do
   it "NativeFunction constant exists" do
     lambda { Rhino::NativeFunction }.should_not raise_error
   end
+
+  it "JavascriptError returns JSError" do
+    lambda { Rhino::JavascriptError.should be(Rhino::JSError) }.should_not raise_error
+  end
   
 end
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diff --git a/spec/rhino/error_spec.rb b/spec/rhino/error_spec.rb
new file mode 100644
index 0000000..63e24cd
--- /dev/null
+++ b/spec/rhino/error_spec.rb
@@ -0,0 +1,38 @@
+require File.expand_path('../spec_helper', File.dirname(__FILE__))
+
+describe Rhino::JSError do
+  
+  it "works as a StandardError with a message being passed" do
+    js_error = Rhino::JSError.new 'an error message'
+    lambda { js_error.to_s && js_error.inspect }.should_not raise_error
+    
+    js_error.cause.should be_nil
+    js_error.message.should == 'an error message'
+    js_error.javascript_backtrace.should be_nil
+  end
+  
+  it "might wrap a RhinoException wrapped in a NativeException like error" do
+    # JRuby's NativeException.new(rhino_e) does not work as it is
+    # intended to handle Java exceptions ... no new on the Ruby side
+    native_error_class = Class.new(RuntimeError) do
+      
+      def initialize(cause)
+        @cause = cause
+      end
+      
+      def cause
+        @cause
+      end
+      
+    end
+    
+    rhino_e = Rhino::JS::JavaScriptException.new("42".to_java)
+    js_error = Rhino::JSError.new native_error_class.new(rhino_e)
+    lambda { js_error.to_s && js_error.inspect }.should_not raise_error
+    
+    js_error.cause.should be(rhino_e)
+    js_error.message.should == '42'
+    js_error.javascript_backtrace.should_not be_nil
+  end
+  
+end
\ No newline at end of file