diff --git a/bigchaindb/web/views/parameters.py b/bigchaindb/web/views/parameters.py
index 9759563e..6eca4a97 100644
--- a/bigchaindb/web/views/parameters.py
+++ b/bigchaindb/web/views/parameters.py
@@ -4,7 +4,7 @@ import re
 def valid_txid(txid):
     if re.match('^[a-fA-F0-9]{64}$', txid):
         return txid.lower()
-    raise ValueError("Invalid hash")
+    raise ValueError('Invalid hash')
 
 
 def valid_bool(val):
@@ -20,7 +20,7 @@ def valid_ed25519(key):
     if (re.match('^[1-9a-zA-Z]{43,44}$', key) and not
        re.match('.*[Il0O]', key)):
         return key
-    raise ValueError("Invalid base58 ed25519 key")
+    raise ValueError('Invalid base58 ed25519 key')
 
 
 def valid_operation(op):
diff --git a/tests/web/test_transactions.py b/tests/web/test_transactions.py
index 6970c725..71f4f0e9 100644
--- a/tests/web/test_transactions.py
+++ b/tests/web/test_transactions.py
@@ -202,12 +202,12 @@ def test_transactions_get_list_good(client):
     asset_id = '1' * 64
 
     with patch('bigchaindb.core.Bigchain.get_transactions_filtered', get_txs_patched):
-        url = TX_ENDPOINT + "?asset_id=" + asset_id
+        url = TX_ENDPOINT + '?asset_id=' + asset_id
         assert client.get(url).json == [
             ['asset_id', asset_id],
             ['operation', None]
         ]
-        url = TX_ENDPOINT + "?asset_id=" + asset_id + "&operation=CREATE"
+        url = TX_ENDPOINT + '?asset_id=' + asset_id + '&operation=CREATE'
         assert client.get(url).json == [
             ['asset_id', asset_id],
             ['operation', 'CREATE']
@@ -220,11 +220,11 @@ def test_transactions_get_list_bad(client):
     with patch('bigchaindb.core.Bigchain.get_transactions_filtered',
                lambda *_, **__: should_not_be_called()):
         # Test asset id validated
-        url = TX_ENDPOINT + "?asset_id=" + '1' * 63
+        url = TX_ENDPOINT + '?asset_id=' + '1' * 63
         assert client.get(url).status_code == 400
         # Test operation validated
-        url = TX_ENDPOINT + "?asset_id=" + '1' * 64 + "&operation=CEATE"
+        url = TX_ENDPOINT + '?asset_id=' + '1' * 64 + '&operation=CEATE'
         assert client.get(url).status_code == 400
         # Test asset ID required
-        url = TX_ENDPOINT + "?operation=CREATE"
+        url = TX_ENDPOINT + '?operation=CREATE'
         assert client.get(url).status_code == 400