diff --git a/trezorlib/tx_api.py b/trezorlib/tx_api.py
index 038ba0abc..1ea9c77d8 100644
--- a/trezorlib/tx_api.py
+++ b/trezorlib/tx_api.py
@@ -30,7 +30,7 @@ class TxApi(object):
         self.url = url
 
     def get_url(self, *args):
-        return "/".join(map(str, [self.url, "api", *args]))
+        return "/".join(map(str, [self.url, "api"] + list(args)))
 
     def fetch_json(self, resource, resourceid):
         global cache_dir