diff --git a/bson/writer/writer.factor b/bson/writer/writer.factor
index 3859f314e2..db452f4029 100644
--- a/bson/writer/writer.factor
+++ b/bson/writer/writer.factor
@@ -3,7 +3,7 @@
 USING: accessors assocs bson.constants byte-arrays fry io io.binary
 io.encodings.binary io.encodings.string io.encodings.utf8
 io.streams.byte-array kernel math math.parser quotations sequences
-serialize strings words ;
+serialize strings words tools.hexdump ;
 
 IN: bson.writer
 
@@ -99,11 +99,13 @@ M: sequence bson-write ( array -- )
     [ [ MDB_OID_FIELD ] dip write-pair ] [ drop ] if ; inline
 
 : skip-field? ( name -- boolean )
-    { MDB_OID_FIELD MDB_INTERNAL_FIELD } member? ; inline
+    { "_id" "_mdb" } member? ; inline
 
 M: assoc bson-write ( assoc -- )
-    '[ _ [ write-oid ] [ [ over skip-field? [ 2drop ] [ write-pair ] if ] assoc-each ] bi ]
-    binary swap with-byte-writer
+    [ binary ] dip
+    '[ _  [ write-oid ] keep
+       [ over skip-field? [ 2drop ] [ write-pair ] if ] assoc-each
+    ] with-byte-writer
     [ length 5 + bson-write ] keep
     write
     write-eoo ; 
diff --git a/mongodb/driver/driver.factor b/mongodb/driver/driver.factor
index d8e90052d0..ee899522cc 100644
--- a/mongodb/driver/driver.factor
+++ b/mongodb/driver/driver.factor
@@ -1,6 +1,6 @@
 USING: accessors assocs fry io.sockets kernel math mongodb.msg formatting linked-assocs destructors continuations
 mongodb.operations namespaces sequences splitting math.parser io.encodings.binary combinators io.streams.duplex
-arrays io memoize constructors sets strings ;
+arrays io memoize constructors sets strings uuid ;
 
 IN: mongodb.driver
 
@@ -231,7 +231,7 @@ M: assoc count
  
 : lasterror ( -- error )
     cmd-collection H{ { "getlasterror" 1 } } <mdb-query-msg>
-    find-one objects>> [ "err" ] at ;
+    find-one objects>> first [ "err" ] dip at ;
 
 GENERIC: validate ( collection -- )
 M: string validate
@@ -262,6 +262,7 @@ M: assoc save-unsafe
 GENERIC: ensure-index ( collection name spec -- )
 M: assoc ensure-index
     H{ } clone
+    [ [ uuid1 "_id" ] dip set-at ] keep
     [ [ "key" ] dip set-at ] keep
     [ [ "name" ] dip set-at ] keep
     [ [ index-ns "ns" ] dip set-at ] keep
diff --git a/mongodb/mmm/mmm.factor b/mongodb/mmm/mmm.factor
index ce942ce67b..467070859e 100644
--- a/mongodb/mmm/mmm.factor
+++ b/mongodb/mmm/mmm.factor
@@ -1,7 +1,7 @@
 USING: accessors fry io io.encodings.binary io.servers.connection
 io.sockets io.streams.byte-array kernel math mongodb.msg classes formatting
-mongodb.msg.private namespaces prettyprint tools.walker calendar calendar.format
-json.writer ;
+namespaces prettyprint tools.walker calendar calendar.format
+json.writer mongodb.operations.private mongodb.operations ;
 
 IN: mongodb.mmm