diff --git a/Rakefile b/Rakefile
index e526d7c1d9..c90e8272f5 100644
--- a/Rakefile
+++ b/Rakefile
@@ -10,6 +10,7 @@ rescue LoadError
 end
 require 'rbconfig'
 include Config
+ENV['TEST_MODE'] = 'TRUE'
 
 gem_command = "gem"
 gem_command = "gem1.9" if $0.match(/1\.9$/) # use gem1.9 if we used rake1.9
diff --git a/lib/mongo.rb b/lib/mongo.rb
index 6f3d70273d..187f6e03cd 100644
--- a/lib/mongo.rb
+++ b/lib/mongo.rb
@@ -8,6 +8,8 @@ module Mongo
 end
 
 begin
+    # Need this for running test with and without c ext in Ruby 1.9.
+    raise LoadError if ENV['TEST_MODE'] && !ENV['C_EXT']
     require 'mongo_ext/cbson'
     require 'mongo/util/bson_c'
     BSON            = BSON_C
@@ -31,6 +33,7 @@ module Mongo
 require 'mongo/util/support'
 require 'mongo/util/conversions'
 require 'mongo/util/server_version'
+require 'mongo/util/bson_ruby'
 
 require 'mongo/errors'
 require 'mongo/constants'
diff --git a/lib/mongo/collection.rb b/lib/mongo/collection.rb
index ab46c0934d..cd498f34dc 100644
--- a/lib/mongo/collection.rb
+++ b/lib/mongo/collection.rb
@@ -216,7 +216,7 @@ def insert(doc_or_docs, options={})
     def remove(selector={})
       message = ByteBuffer.new
       message.put_int(0)
-      BSON.serialize_cstr(message, "#{@db.name}.#{@name}")
+      BSON_RUBY.serialize_cstr(message, "#{@db.name}.#{@name}")
       message.put_int(0)
       message.put_array(BSON_SERIALIZER.serialize(selector, false).unpack("C*"))
       @connection.send_message(Mongo::Constants::OP_DELETE, message,
@@ -243,7 +243,7 @@ def remove(selector={})
     def update(selector, document, options={})
       message = ByteBuffer.new
       message.put_int(0)
-      BSON.serialize_cstr(message, "#{@db.name}.#{@name}")
+      BSON_RUBY.serialize_cstr(message, "#{@db.name}.#{@name}")
       update_options  = 0
       update_options += 1 if options[:upsert]
       update_options += 2 if options[:multi]
@@ -507,7 +507,7 @@ def normalize_hint_fields(hint)
     def insert_documents(documents, collection_name=@name, check_keys=true, safe=false)
       message = ByteBuffer.new
       message.put_int(0)
-      BSON.serialize_cstr(message, "#{@db.name}.#{collection_name}")
+      BSON_RUBY.serialize_cstr(message, "#{@db.name}.#{collection_name}")
       documents.each { |doc| message.put_array(BSON_SERIALIZER.serialize(doc, check_keys).unpack("C*")) }
       if safe
         @connection.send_message_with_safe_check(Mongo::Constants::OP_INSERT, message, @db.name,
diff --git a/lib/mongo/connection.rb b/lib/mongo/connection.rb
index 17fbe6ee78..32f23a930c 100644
--- a/lib/mongo/connection.rb
+++ b/lib/mongo/connection.rb
@@ -467,7 +467,7 @@ def read_documents(number_received, cursor_id, sock)
     def last_error_message(db_name)
       message = ByteBuffer.new
       message.put_int(0)
-      BSON.serialize_cstr(message, "#{db_name}.$cmd")
+      BSON_RUBY.serialize_cstr(message, "#{db_name}.$cmd")
       message.put_int(0)
       message.put_int(-1)
       message.put_array(BSON_SERIALIZER.serialize({:getlasterror => 1}, false).unpack("C*"))
diff --git a/lib/mongo/cursor.rb b/lib/mongo/cursor.rb
index bdf916acca..6284331f9b 100644
--- a/lib/mongo/cursor.rb
+++ b/lib/mongo/cursor.rb
@@ -286,7 +286,7 @@ def refill_via_get_more
 
       # DB name.
       db_name = @admin ? 'admin' : @db.name
-      BSON.serialize_cstr(message, "#{db_name}.#{@collection.name}")
+      BSON_RUBY.serialize_cstr(message, "#{db_name}.#{@collection.name}")
 
       # Number of results to return; db decides for now.
       message.put_int(0)
@@ -317,7 +317,7 @@ def construct_query_message
       message = ByteBuffer.new
       message.put_int(query_opts)
       db_name = @admin ? 'admin' : @db.name
-      BSON.serialize_cstr(message, "#{db_name}.#{@collection.name}")
+      BSON_RUBY.serialize_cstr(message, "#{db_name}.#{@collection.name}")
       message.put_int(@skip)
       message.put_int(@limit)
       selector = @selector
diff --git a/lib/mongo/util/bson_c.rb b/lib/mongo/util/bson_c.rb
index 4c3d640cb6..d6b349a016 100644
--- a/lib/mongo/util/bson_c.rb
+++ b/lib/mongo/util/bson_c.rb
@@ -1,25 +1,6 @@
 # A thin wrapper for the CBson class
 class BSON_C
 
-  if RUBY_VERSION >= '1.9'
-    def self.to_utf8(str)
-      str.encode("utf-8")
-    end
-  else
-    def self.to_utf8(str)
-      begin
-      str.unpack("U*")
-      rescue => ex
-        raise InvalidStringEncoding, "String not valid utf-8: #{str}"
-      end
-      str
-    end
-  end
-
-  def self.serialize_cstr(buf, val)
-    buf.put_array(to_utf8(val.to_s).unpack("C*") + [0])
-  end
-
   def self.serialize(obj, check_keys=false)
     ByteBuffer.new(CBson.serialize(obj, check_keys))
   end
@@ -34,12 +15,4 @@ def self.deserialize(buf=nil)
     CBson.deserialize(buf.to_s)
   end
 
-  def deserialize(buf=nil)
-    self.class.deserialize(buf)
-  end
-
-  def serialize(buf, check_keys=false)
-    self.class.serialize(buf, check_keys)
-  end
-
 end
diff --git a/lib/mongo/util/bson_ruby.rb b/lib/mongo/util/bson_ruby.rb
index 6c1f5d4e98..078de1591f 100644
--- a/lib/mongo/util/bson_ruby.rb
+++ b/lib/mongo/util/bson_ruby.rb
@@ -69,7 +69,7 @@ def self.to_utf8(str)
   end
 
   def self.serialize_cstr(buf, val)
-    buf.put_array(to_utf8(val.to_s).unpack("C*") + [0])
+    buf.put_array(to_utf8(val.to_s).unpack("C*") << 0)
   end
 
   def to_a
diff --git a/test/test_bson.rb b/test/test_bson.rb
index c243322d31..964a102146 100644
--- a/test/test_bson.rb
+++ b/test/test_bson.rb
@@ -1,35 +1,31 @@
+# coding:utf-8
 require 'test/test_helper'
-require 'iconv'
 
 class BSONTest < Test::Unit::TestCase
 
   include Mongo
 
-  def setup
-    # We don't pass a DB to the constructor, even though we are about to test
-    # deserialization. This means that when we deserialize, any DBRefs will
-    # have nil @db ivars. That's fine for now.
-    #BSON = BSON.new
-  end
-
   def test_string
     doc = {'doc' => 'hello, world'}
     bson = bson = BSON.serialize(doc)
     assert_equal doc, BSON.deserialize(bson)
   end
 
-
   def test_valid_utf8_string
-    doc = {'doc' => "aéあ"}
+    doc = {'doc' => "aé"}
     bson = bson = BSON.serialize(doc)
     assert_equal doc, BSON.deserialize(bson)
   end
 
-  def test_invalid_string
-    string = Iconv.conv('iso-8859-1', 'utf-8', 'aé').first
-    doc = {'doc' => string} 
-    assert_raise InvalidStringEncoding do
-      BSON.serialize(doc)
+  # We'll raise this exception only in 1.8 since 1.9 forces UTF-8 conversion.
+  if RUBY_VERSION < '1.9'
+    require 'iconv'
+    def test_invalid_string
+      string = Iconv.conv('iso-8859-1', 'utf-8', 'aé').first
+      doc = {'doc' => string} 
+      assert_raise InvalidStringEncoding do
+        BSON.serialize(doc)
+      end
     end
   end