diff --git a/bigchaindb/lib.py b/bigchaindb/lib.py
index 4c45beda..444a5a95 100644
--- a/bigchaindb/lib.py
+++ b/bigchaindb/lib.py
@@ -225,13 +225,10 @@ class BigchainDB(object):
             return backend.query.delete_unspent_outputs(
                                         self.connection, *unspent_outputs)
 
-    def is_commited(self, transaction_id):
+    def is_committed(self, transaction_id):
         transaction = backend.query.get_transaction(self.connection, transaction_id)
-        if transaction:
-            return True
-        else:
-            return False
-        
+        return bool(transaction)
+
     def get_transaction(self, transaction_id):
         transaction = backend.query.get_transaction(self.connection, transaction_id)
 
diff --git a/bigchaindb/models.py b/bigchaindb/models.py
index 56c26e28..9df4dbd4 100644
--- a/bigchaindb/models.py
+++ b/bigchaindb/models.py
@@ -27,7 +27,7 @@ class Transaction(Transaction):
 
         if self.operation == Transaction.CREATE:
             duplicates = any(txn for txn in current_transactions if txn.id == self.id)
-            if bigchain.is_commited(self.id) or duplicates:
+            if bigchain.is_committed(self.id) or duplicates:
                 raise DuplicateTransaction('transaction `{}` already exists'
                                            .format(self.id))