diff --git a/HISTORY b/HISTORY
index acf0997..ebee923 100644
--- a/HISTORY
+++ b/HISTORY
@@ -3,22 +3,32 @@
   * Collection#find_and_modify
   * Collection#stats
   * DB#stats
-* Exception class adjustments:
-  * Mongo::InvalidObjectID moved to BSON::InvalidObjectID
-  * Mongo::InvalidDocument moved to BSON::InvalidDocument
-  * Mongo::InvalidStringEncoding moved to BSON::InvalidStringEncoding
-  * Mongo::InvalidName replaced by Mongo::InvalidNSName and BSON::InvalidKeyName
-* BSON-related code extracted into two separate gems: bson and bson_ext (Chuck Remes).
-* Extensions compile on Rubinius (Chuck Remes).
 * Query :fields options allows for values of 0 to exclude fields (houdini, railsjedi).
-* BSON::Binary constructor can now take a string, which will be packed into an array.
 * GridFS
   * Option to delete old versions of GridFileSystem entries.
   * Filename is now optional for Grid#put.
   * Option to write arbitrary attributes to a file: @grid.put(@data, :favorite_phrase => "blimey!")
+  * Indexes created on the chunks collection are now unique. If you have an existing chunks collection,
+    you may want to remove 
 * Removed the following deprecated items:
   * GridStore class
 
+* BSON-related code extracted into two separate gems: bson and bson_ext (thx to Chuck Remes).
+  * mongo_ext no longer exists.
+  * BSON::Binary constructor can now take a string, which will be packed into an array.
+  * Exception class adjustments:
+    * Mongo::InvalidObjectID moved to BSON::InvalidObjectID
+    * Mongo::InvalidDocument moved to BSON::InvalidDocument
+    * Mongo::InvalidStringEncoding moved to BSON::InvalidStringEncoding
+    * Mongo::InvalidName replaced by Mongo::InvalidNSName and BSON::InvalidKeyName
+  * BSON types are now namespaced under the BSON module. These types include:
+    * Binary
+    * ObjectID
+    * Code
+    * DBRef
+    * MinKey and MaxKey
+  * Extensions compile on Rubinius (Chuck Remes).
+
 0.19.3 2010-4-5
 * Minor fix for assert_valid_keys.
 
diff --git a/lib/mongo/gridfs/grid.rb b/lib/mongo/gridfs/grid.rb
index cc9750d..7db8e16 100644
--- a/lib/mongo/gridfs/grid.rb
+++ b/lib/mongo/gridfs/grid.rb
@@ -34,7 +34,7 @@ module Mongo
       @chunks  = @db["#{fs_name}.chunks"]
       @fs_name = fs_name
 
-      @chunks.create_index([['files_id', Mongo::ASCENDING], ['n', Mongo::ASCENDING]])
+      @chunks.create_index([['files_id', Mongo::ASCENDING], ['n', Mongo::ASCENDING]], :unique => true)
     end
 
     # Store a file in the file store.
diff --git a/lib/mongo/gridfs/grid_file_system.rb b/lib/mongo/gridfs/grid_file_system.rb
index 3d37e94..bdf358c 100644
--- a/lib/mongo/gridfs/grid_file_system.rb
+++ b/lib/mongo/gridfs/grid_file_system.rb
@@ -34,8 +34,10 @@ module Mongo
       @chunks  = @db["#{fs_name}.chunks"]
       @fs_name = fs_name
 
-      @files.create_index([['filename', 1], ['uploadDate', -1]])
       @default_query_opts = {:sort => [['filename', 1], ['uploadDate', -1]], :limit => 1}
+
+      @files.create_index([['filename', 1], ['uploadDate', -1]])
+      @chunks.create_index([['files_id', Mongo::ASCENDING], ['n', Mongo::ASCENDING]], :unique => true)
     end
 
     # Open a file for reading or writing. Note that the options for this method only apply
diff --git a/test/grid_file_system_test.rb b/test/grid_file_system_test.rb
index cd30f02..fb2c420 100644
--- a/test/grid_file_system_test.rb
+++ b/test/grid_file_system_test.rb
@@ -30,6 +30,14 @@ class GridFileSystemTest < Test::Unit::TestCase
         assert_equal data.length, @chunks_data.length
       end
 
+      should "have a unique index on chunks" do
+        assert @db['fs.chunks'].index_information['files_id_1_n_1']['unique']
+      end
+
+      should "have an index on filename" do
+        assert @db['fs.files'].index_information['filename_1_uploadDate_-1']
+      end
+
       should "return an empty string if length is zero" do
         data = @grid.open('sample.file', 'r') { |f| f.read(0) }
         assert_equal '', data
diff --git a/test/grid_test.rb b/test/grid_test.rb
index 63432e2..e3c7f2c 100644
--- a/test/grid_test.rb
+++ b/test/grid_test.rb
@@ -27,6 +27,10 @@ class GridTest < Test::Unit::TestCase
         assert_equal @data, data
       end
 
+      should "have a unique index on chunks" do
+        assert @chunks.index_information['files_id_1_n_1']['unique']
+      end
+
       should "store the filename" do
         file = @grid.get(@id)
         assert_equal 'sample', file.filename