diff --git a/pysearpc/client.py b/pysearpc/client.py
index 9333a5c..a57167d 100644
--- a/pysearpc/client.py
+++ b/pysearpc/client.py
@@ -17,9 +17,11 @@ def _fret_int(ret_str):
         
     if dicts.has_key('err_code'):
         raise SearpcError(dicts['err_msg'])
-        
-    if dicts['ret']:
+
+    if dicts.has_key('ret'):
         return dicts['ret']
+    else:
+        raise SearpcError('Invalid response format')
 
 def _fret_string(ret_str):
     try: