diff --git a/python/transmitter/gsm_gmsk_mod.py b/python/transmitter/gsm_gmsk_mod.py
index e8ecc7a..fec936c 100644
--- a/python/transmitter/gsm_gmsk_mod.py
+++ b/python/transmitter/gsm_gmsk_mod.py
@@ -14,7 +14,7 @@
 from gnuradio.filter import firdes
 import grgsm
 
-class gsm_gmsk_mod(grgsm.hier_block):
+class gsm_gmsk_mod(gr.hier_block2):
 
     def __init__(self, BT=4, pulse_duration=4, sps=4):
         gr.hier_block2.__init__(