diff --git a/neurodamus/core/stimuli.py b/neurodamus/core/stimuli.py
index 77348aca..f9293d95 100644
--- a/neurodamus/core/stimuli.py
+++ b/neurodamus/core/stimuli.py
@@ -437,16 +437,16 @@ def __init__(self, cell_section, position=0.5, clamp_container=None,
             
             
             # Check sif new conductanceSource mechanism is available
-            mt = h.MechanismType(1)
-            mname = h.ref('')
+            mt = Neuron.h.MechanismType(1)
+            mname = Neuron.h.ref('')
             mList = []
             for i in range(mt.count()):
                 mt.select(i)
                 mt.selected(mname)
                 mList.append(mname[0])
                                 
-            if 'conductanceSource' in mList
-            
+            if 'conductanceSource' in mList:
+
                 self.clamp = Neuron.h.conductanceSource(position, sec=cell_section)
             
             else:
diff --git a/neurodamus/stimulus_manager.py b/neurodamus/stimulus_manager.py
index f0e711c0..424f9051 100644
--- a/neurodamus/stimulus_manager.py
+++ b/neurodamus/stimulus_manager.py
@@ -755,8 +755,8 @@ def __init__(self, target, stim_info: dict, cell_manager):
                 # create single electrode voltage clamp at location
                 
                 # Checks if new conductanceSource mechanism is available
-                mt = h.MechanismType(1)
-                mname = h.ref('')
+                mt = Nd.h.MechanismType(1)
+                mname = Nd.h.ref('')
                 mList = []
                 for i in range(mt.count()):
                     mt.select(i)