diff --git a/bigchaindb/lib.py b/bigchaindb/lib.py
index 64d4e1ba..2dadcb90 100644
--- a/bigchaindb/lib.py
+++ b/bigchaindb/lib.py
@@ -100,9 +100,14 @@ class BigchainDB(object):
 
         error = response.get('error')
         if error:
+            status_code = 500
             message = error.get('message', 'Internal Error')
             data = error.get('data', '')
-            return (400, message + ' - ' + data)
+
+            if 'Tx already exists in cache' in data:
+                status_code = 400
+
+            return (status_code, message + ' - ' + data)
 
         result = response['result']
         if mode == self.mode_commit: