diff --git a/lib/ucoinpy/api/bma/tx/__init__.py b/lib/ucoinpy/api/bma/tx/__init__.py
index 384b7ff9f0b8827ae1ac2e400e1adc91efef2b48..10ea07a5ca4bf673286a3b4d36dbf76662e85d22 100644
--- a/lib/ucoinpy/api/bma/tx/__init__.py
+++ b/lib/ucoinpy/api/bma/tx/__init__.py
@@ -44,4 +44,4 @@ class Sources(Tx):
 
     def __get__(self, **kwargs):
         assert self.pubkey is not None
-        return self.requests_get('/sources/%d' % self.pubkey, **kwargs).json()
+        return self.requests_get('/sources/%s' % self.pubkey, **kwargs).json()