diff --git a/QGL/PulsePrimitives.py b/QGL/PulsePrimitives.py
index 24408a3e..25f00f40 100644
--- a/QGL/PulsePrimitives.py
+++ b/QGL/PulsePrimitives.py
@@ -73,11 +73,10 @@ def Ztheta(qubit, angle=0, label='Ztheta', **kwargs):
     # special cased because it can be done with a frame update
     Zprod = TAPulse(label, qubit, length=0, amp=0, phase=0, frameChange=-angle)
     if hasattr(ChannelLibrary.channelLib,"connectivityG"):
-        for node in ChannelLibrary.channelLib.connectivityG.nodes():
-            #shift the reference for all CR gates with qubit as the target
-            if ChannelLibrary.channelLib.connectivityG.has_predecessor(qubit,node):
-                CRchan = ChannelLibrary.channelLib.connectivityG.edge[node][qubit]['channel']
-                Zprod = Zprod*TAPulse(label, CRchan, length=0, amp=0, phase=0, frameChange=-angle)
+    #shift the reference for all CR gates with qubit as the target
+        for predecessor in ChannelLibrary.channelLib.connectivityG.predecessors(qubit):
+            CRchan = ChannelLibrary.channelLib.connectivityG.edge[predecessor][qubit]['channel']
+            Zprod = Zprod*TAPulse(label, CRchan, length=0, amp=0, phase=0, frameChange=-angle)
     return Zprod
 
 #Setup the default 90/180 rotations