diff --git a/bigchaindb/consensus.py b/bigchaindb/consensus.py
index c44b98fd..2f803c60 100644
--- a/bigchaindb/consensus.py
+++ b/bigchaindb/consensus.py
@@ -131,32 +131,26 @@ class BaseConsensusRules(AbstractConsensusRules):
 
         else:
             # check if the input exists, is owned by the current_owner
-            if not transaction['transaction']['inputs']:
+            if not transaction['transaction']['fulfillments']:
                 raise ValueError(
-                    'Only `CREATE` transactions can have null inputs')
+                    'Transaction contains no fulfillments')
 
             # check inputs
-            for inp in transaction['transaction']['inputs']:
-                tx_input = bigchain.get_transaction(inp)
+            for fulfillment in transaction['transaction']['fulfillments']:
+                tx_input = bigchain.get_transaction(fulfillment['input']['txid'])
 
                 if not tx_input:
                     raise exceptions.TransactionDoesNotExist(
                         'input `{}` does not exist in the bigchain'.format(
-                            transaction['transaction']['input']))
-
-                if (tx_input['transaction']['new_owner'] !=
-                    transaction['transaction']['current_owner']):
-                    raise exceptions.TransactionOwnerError(
-                        'current_owner `{}` does not own the input `{}`'.format(
-                            transaction['transaction']['current_owner'],
-                            transaction['transaction']['input']))
+                            fulfillment['input']['txid']))
 
                 # check if the input was already spent by a transaction other than
                 # this one.
-                spent = bigchain.get_spent(tx_input['id'])
+                spent = bigchain.get_spent(fulfillment['input'])
+                print(spent)
                 if spent and spent['id'] != transaction['id']:
                     raise exceptions.DoubleSpend(
-                        'input `{}` was already spent'.format(inp))
+                        'input `{}` was already spent'.format(fulfillment['input']))
 
         # Check hash of the transaction
         # remove the fulfillment messages (signatures)
diff --git a/bigchaindb/core.py b/bigchaindb/core.py
index 2612c1ed..b4ac1644 100644
--- a/bigchaindb/core.py
+++ b/bigchaindb/core.py
@@ -186,29 +186,31 @@ class Bigchain(object):
         transactions = list(cursor)
         return transactions
 
-    def get_spent(self, txid):
+    def get_spent(self, inp):
         """Check if a `txid` was already used as an input.
 
         A transaction can be used as an input for another transaction. Bigchain needs to make sure that a
         given `txid` is only used once.
 
         Args:
-            txid (str): transaction id.
+            inp (dict): Input of a transaction in the form `{'txid': 'transaction id', 'cid': 'condition id'}`
 
         Returns:
             The transaction that used the `txid` as an input if it exists else it returns `None`
         """
         # checks if an input was already spent
-        # checks if the bigchain has any transaction with input `transaction_id`
-        response = r.table('bigchain').concat_map(lambda doc: doc['block']['transactions']) \
-            .filter(lambda transaction: transaction['transaction']['inputs'].contains(txid)).run(self.conn)
+        # checks if the bigchain has any transaction with input {'txid': ..., 'cid': ...}
+        response = r.table('bigchain').concat_map(lambda doc: doc['block']['transactions'])\
+            .filter(lambda transaction: transaction['transaction']['fulfillments']
+                    .contains(lambda fulfillment: fulfillment['input'] == inp))\
+            .run(self.conn)
 
         # a transaction_id should have been spent at most one time
         transactions = list(response)
         if transactions:
             if len(transactions) != 1:
                 raise Exception('`{}` was spent more then once. There is a problem with the chain'.format(
-                    txid))
+                    inp['txid']))
             else:
                 return transactions[0]
         else:
diff --git a/bigchaindb/util.py b/bigchaindb/util.py
index d6f87751..e63aa1d1 100644
--- a/bigchaindb/util.py
+++ b/bigchaindb/util.py
@@ -221,7 +221,7 @@ def create_tx(current_owners, new_owners, inputs, operation, payload=None):
     return transaction
 
 
-#TODO: Change sign_tx to populate the fulfillments
+# TODO: Change sign_tx to populate the fulfillments
 def sign_tx(transaction, private_key):
     """Sign a transaction
 
@@ -261,7 +261,7 @@ def sign_tx(transaction, private_key):
             # update the fulfillment message
             fulfillment_message.update({
                 'input': fulfillment['input'],
-                'condition': conditions[fulfillment['cid']]
+                'condition': conditions[fulfillment['fid']]
             })
 
         # sign the fulfillment message
@@ -322,7 +322,7 @@ def verify_signature(signed_transaction):
             # get previous condition
             previous_tx = b.get_transaction(fulfillment['input']['txid'])
             conditions = sorted(previous_tx['transaction']['conditions'], key=lambda d: d['cid'])
-            fulfillment_message['condition'] = conditions[fulfillment['cid']]
+            fulfillment_message['condition'] = conditions[fulfillment['fid']]
 
         # verify the signature (for now lets assume there is only one owner)
         vk = crypto.VerifyingKey(fulfillment['current_owners'][0])