diff --git a/zinc/client.py b/zinc/client.py
index e7db6f0..b3d5594 100644
--- a/zinc/client.py
+++ b/zinc/client.py
@@ -47,7 +47,7 @@ def _req(self,method,url,data=None):
         if data: logger.debug('Request data: %s',self._pjs(data))
 
         r = getattr(requests,method)(fullurl,**kwargs).json
-        if isinstance(r,type(lambda:0)): r = r() # new requests uses r.json()
+        if hasattr(r, '__call__'): r = r() # new requests uses r.json()
 
         try:
             logger.debug('Response data: %s',self._pjs(r))