diff --git a/bigchaindb/backend/mongodb/changefeed.py b/bigchaindb/backend/mongodb/changefeed.py
index 34650df3..d52927b9 100644
--- a/bigchaindb/backend/mongodb/changefeed.py
+++ b/bigchaindb/backend/mongodb/changefeed.py
@@ -34,11 +34,6 @@ class MongoDBChangeFeed(ChangeFeed):
                 time.sleep(1)
 
     def run_changefeed(self):
-        # this is kinda a hack to make sure that the connection object is
-        # setup
-        self.connection._connect()
-        # namespace to allow us to only listen to changes in a single
-        # collection
         dbname = self.connection.dbname
         table = self.table
         namespace = '{}.{}'.format(dbname, table)
@@ -61,24 +56,29 @@ class MongoDBChangeFeed(ChangeFeed):
                 record = cursor.next()
             except StopIteration:
                 continue
-            else:
-                is_insert = record['op'] == 'i'
-                is_delete = record['op'] == 'd'
-                is_update = record['op'] == 'u'
 
-                if is_insert and (self.operation & ChangeFeed.INSERT):
-                    self.outqueue.put(record['o'])
-                elif is_delete and (self.operation & ChangeFeed.DELETE):
-                    # on delete it only returns the id of the document
-                    self.outqueue.put(record['o'])
-                elif is_update and (self.operation & ChangeFeed.UPDATE):
-                    # the oplog entry for updates only returns the update
-                    # operations to apply to the document and not the
-                    # document itself. So here we first read the document
-                    # and then return it
-                    doc = self.connection.conn[dbname][table]\
-                              .find_one(record['o2'])
-                    self.outqueue.put(doc)
+            is_insert = record['op'] == 'i'
+            is_delete = record['op'] == 'd'
+            is_update = record['op'] == 'u'
+
+            # mongodb documents uses the `_id` for the primary key.
+            # We are not using this field at this point and we need to
+            # remove it to prevent problems with schema validation.
+            # See https://github.com/bigchaindb/bigchaindb/issues/992
+            if is_insert and (self.operation & ChangeFeed.INSERT):
+                record['o'].pop('_id', None)
+                doc = record['o']
+            elif is_delete and (self.operation & ChangeFeed.DELETE):
+                # on delete it only returns the id of the document
+                doc = record['o']
+            elif is_update and (self.operation & ChangeFeed.UPDATE):
+                # the oplog entry for updates only returns the update
+                # operations to apply to the document and not the
+                # document itself. So here we first read the document
+                # and then return it.
+                doc = self.connection.conn[dbname][table]\
+                        .find_one(record['o2'], projection={'_id': False})
+            self.outqueue.put(doc)
 
 
 @register_changefeed(MongoDBConnection)
diff --git a/bigchaindb/pipelines/block.py b/bigchaindb/pipelines/block.py
index 7dda6578..d5c81741 100644
--- a/bigchaindb/pipelines/block.py
+++ b/bigchaindb/pipelines/block.py
@@ -44,8 +44,6 @@ class BlockPipeline:
         if tx['assignee'] == self.bigchain.me:
             tx.pop('assignee')
             tx.pop('assignment_timestamp')
-            # required for mongodb
-            tx.pop('_id', None)
             return tx
 
     def validate_tx(self, tx):